Above the Fold
An expression that refers to the upper half of the front page of a newspaper, or the top third of a brochure or letter that will be folded. In web design, it refers to the section of a web page that is visible without scrolling.
Folding paper by bending each fold in the opposite direction of the previous fold creating a pleated or accordion effect. Also known as Concertina fold or Z-fold.
A paper containing no acidity or acid producing chemicals that degrades less over time than acidic papers.
Against the Grain
At right angles to the grain direction of the paper being used, as compared to with the grain. Also called across the grain and cross grain
Abbreviation for Adobe Illustrator – Popular drawing program for Macintosh and PC. The name also refers to the corresponding file format.
Any change made by the customer after copy or artwork has been given to the service bureau, separator or printer. The change could be in copy, specifications or both. Also called AA, author alteration and customer alteration.
The process of averaging between pixels of different colours. This results is a smoother, more blended transition between the edge of two areas rather than a distinctly jagged appearance.
Fine powder lightly sprayed over the printed surface of coated paper as sheets leave a press. Also called dust, offset powder, powder and spray powder.
This clear coating is used to protect printed pieces. It provides a high-gloss surface that deters dirt and fingerprints. Aqueous coating improves the durability of postcards as they go through the mail, and protects business cards as they ride around in people's pockets. It also looks beautiful on brochures, catalog covers, and stand-alone flyers.
Any part of a lower case letter which rises above the main body of the letter such as in "d", "b" and "h".
Abbreviation for Black and White
(1) To print on the second side of a sheet already printed on one side.
(2) To adjust an image on one side of a sheet so that it aligns back-to-back with an image on the other side.
The imaginary horizontal line upon which stand capitals, lower case letters, punctuation points, etc.
Usually in the book arena, but not exclusively, the joining of leafs or signatures together with either wire, glue or other means.
Usually a department within a printing company responsible for collating, folding and trimming various printing projects.
A digital image that uses a grid of picture elements (pixels). Every pixel uses a number of bits to determine its colour. A 1 bit bitmap only contains black-and-white pixels, a 24 bit bitmap is a picture that can contain up to 16 million different colours.
The rubberised surfaced material secured onto a cylinder onto which the ink is transferred from the plate and then to the paper.
Printing that extends to the edge of a sheet or page after trimming.
Image debossed, embossed or stamped, but not printed with ink or foil.
Abbreviation for BitMaP – A graphic file format for Windows that is not really suitable for prepress use.
General term for paper over 200gsm that is commonly used for products such as presentation folders, business cards, displays and postcards.
Category of paper commonly used for writing, printing and photocopying. Also called laser, business paper, communication paper, correspondence paper and writing paper.
Folded signatures gathered, sewn and trimmed, but not yet covered.
Thickness of paper relative to its basic weight.
Burst Perfect Bind
To bind by forcing glue into notches milled along the spines of gathered signatures, before affixing a paper cover. Also called burst bind, notch bind and slotted bind.
Register where ink colours meet precisely without overlapping or allowing space between, as compared to lap register. Also called butt fit and kiss register.
The process of adjusting a device or process to match certain criteria. This is usually done by measuring the devices’ deviation from standard values and then, during operation of the device, applying values to compensate the deviation. In prepress, in particular, calibration is the fine-tuning of scanners, monitors, printers, and imagesetters in order to increase the accuracy of their output.
(1) Thickness of paper or other substrate expressed in thousandths of a millimetre (microns), inches (points), pages per inch (ppi) or pages per centimeter (ppc).
(2) Device on a sheetfed press that detects double sheets or on a binding machine that detects missing signatures or inserts.
Paper coated with chemicals that enable transfer of images from one sheet to another with pressure from writing or typing. Also known as NCR (no-carbon-required).
To bind using glue to hold signatures to a case made of binder board covered with fabric, plastic or leather. Also called cloth bind, edition bind, hard bind and hard cover.
High gloss, coated paper made by pressing the paper against a polished, hot, metal drum while the coating is still wet. Usually the second side is uncoated.
The two pages that face each other in the centre of a book or publication.
An image processing function that is used to duplicate a pixel or many pixels from one area of a picture to another picture area. This pixel manipulation may add or remove detail. Some people call this function pixel swapping.
Abbreviation for cyan, magenta, yellow and key (black), the four process colours.
Paper with a coating of clay and other substances that improves reflectivity and ink holdout. Paper mills produce coated paper in the four major categories cast, gloss and matte.
Where a metal or plastic wire is spiralled through holes punched along the side of a stack of paper. Commonly used for reports, proposals and manuals. Documents bound with coil have the ability to lay flat and can rotate 360 degrees. Also called spiral binding.
To gather sheets or printed signatures together in their correct order.
Using a computer to adjust, change or manipulate a colour image, such as retouching, adjusting colour balance, colour saturation, contrast, etc.
Colour Control bar
Strip of small blocks of colour on a proof or press sheet to help evaluate features such as density and dot gain. Also called colour bar, colour guide and standard offset colour bar.
The entire range of hues possible to reproduce using a specific device, such as a computer screen, or system, such as four-colour process printing.
Order in which inks are printed. Also called laydown sequence and rotation.
Change in image colour resulting from changes in register, ink densities or dot gain during four-colour process printing.
To bind by inserting the teeth of a flexible plastic comb through holes punched along the edge of a stack of paper. Also called plastic bind.
A narrow, elongated typeface.
The extent to which printing ink covers the surface of a printed sheet. Ink coverage is frequently expressed as light, medium or heavy.
Phenomenon of middle pages of a folded signature extending slightly beyond outside pages. Also called feathering, outpush, push out and thrust.
Lines near the edges of an image indicating portions to be reproduced. Also called cut marks and tic marks.
Abbreviation for Computer to Plate
To dry inks, varnishes or other coatings after printing to ensure good adhesion and prevent setoff.
One of the four process colours. Also known as process blue.
An essential part of the offset printing process whereby rollers distribute a solution to the plate that covers the non-printing area of the plate, repelling ink in those areas. Some newer presses use a waterless ink technology that does not use dampening.
Instrument used to measure density. Reflection densitometers measure light reflected from paper and other surfaces; transmission densitometers measure light transmitted through film and other materials.
The visual darkness of a material caused by its capability to absorb or reflect the light illuminating the material. Density is measured with a densitometer. Coloured materials are measured through their complementary filters. Density differences are sometimes called grey levels. As density increases the amount or reflected or transmitted light is reduced. The amount of light absorbed is inversely proportional to the amount of light from or transmitted through the sample.
The process of cutting paper in a shape or design by the use of a wooden die or block in which are positioned steel rules in the shape of the desired pattern.
The process of averaging between pixels of different colours. This results in a smoother, blended transition between the edge of two areas rather than a jagged or 'stair-step' appearance. Also a method used on ink jet printers where colours are produced by mixing coloured dots in a randomised pattern.
Phenomenon of halftone dots printing larger on paper than they are on films or plates, reducing detail and lowering contrast. Also called dot growth, dot spread and press gain.
Measure of resolution of input devices such as scanners, display devices such as monitors, and output devices such as laser printers, imagesetters and monitors. Abbreviated DPI
The drilling of holes into paper for ring or comb binding.
Thick paper made by pasting highlights together two thinner sheets, usually of different colours. Also called double-faced paper and two-tone paper.
A photographic looking colour print created by heating dyes on a substrate instead of using inks.
In prepress embedding is the process of including data such as fonts or graphics in a file. For example: images can be embedded in an InDesign layout file and fonts can be embedded in a PDF file.
To press an image into paper so it lies above the surface.
Sheet that attaches the inside pages of a case bound book to its cover. Also called pastedown or end sheet.
Encapsulated PostScript file. A computer file containing both images and PostScript commands.
An ink colour added to a printed piece in addition to the standard cyan, magenta, yellow and black used in 4 colour process printing. Usually a Pantone spot colour or custom formulated ink. Requires an extra run through the press on a four colour press adding to the cost. Some presses have five units to accommodate fifth colours or clear coatings.
Screen with ruling of 150 lines per inch (80 lines per centimetre) or more.
The surface quality of a paper.
Size of product after production is completed, as compared to flat size. Also called trimmed size.
Refers to ability of film to be registered during stripping and assembly. Good fit means that all images register to other film for the same job.
Size of product after printing and trimming, but before folding, as compared to finished size.
The process by which overlapping, non-opaque objects are remapped into opaque objects that render with the same look as the original non-opaque objects. This technique is used to support the transparency effects that many current applications offer, on RIPs that do not have native support for this effect.
To print a sheet completely with an ink or varnish. flooding with ink is also called painting the sheet.
Then metal sheet that is applied to paper using the foil stamping process. Frequently gold coloured, but available in many colours.
Stamping a thin sheet of metallic foil onto a sheet of paper and then embossing a pattern under it, creating a three dimensional raised area, usually text or an image.
With printed matter, markings indicating where a fold is to occur, usually located at the top edges.
Gatefold sheet bound into a publication, often used for a map or chart. Also called gatefold and pullout.
Roller(s) that come in contact with the printing plate, bringing it ink or water.
Mixture of water and chemicals that dampens a printing plate to prevent ink from adhering to the non-image area. Also called dampener solution.
Four-colour Process Printing
Technique of printing that uses black, magenta, cyan and yellow to simulate full-colour images. Also called colour process printing, full colour printing and process printing.
A certificate which guarantees that the wood pulp used to produce paper is from sustainably managed forests.
Running off any number of different jobs on the same sheet. After printing, the sheet is cut into individual jobs and the cost pro-rated. Although more cost effective, the downside of this process is that colour accuracy is compromised to achieve average colour across the entire sheet for all the jobs, rather than correct colour for the one job printed on the sheet.
A three or four panel fold where the two outside panels fold inward to meet in the centre. In an open gate fold, there are three panels, the bottom of which is twice the size of the folded panels. In a closed gatefold, there are four panels of roughly equal size where the outer panels are folded inward together.
An image which appears as a lighter area on a subsequent print due to local blanket depressions from previous image areas on a letterpress rotary machine as well as on an offset press.
The process of applying a metallic foil as a decorative element. Silver or gold foil are sometimes applied to the outer edges of books or business cards to conjure up luxury and elegance. Book covers or cosmetics packaging can feature gilded text to make the product stand out.
Direction of fibres in a sheet of paper governing paper properties such as increased size changes with relative humidity, across the grain, and better folding properties along the grain.
A series of metal fingers that hold each sheet of paper as it passes through the various stages of the printing process.
Abbreviation for Grams per Square Meter – a unit of measurement for paper weight.
The inside space between pages, usually the inside margin toward the back or binding edge of a book is meant but for impositioning programs any space between pages is a gutter.
Subjective term referring to very small space, thin line or close register. The meaning depends on who is using the term and in what circumstances.
(1) To photograph or scan a continuous tone image to convert the image into halftone dots.
(2) A photograph or continuous-tone illustration that has been halftoned and appears on film, paper, printing plate or the final printed product.
Imposition with heads (tops) of pages facing tails (bottoms) of other pages.
Spot or imperfection in printing, most visible in areas of heavy ink coverage, caused by dirt on the plate or blanket. Also called bulls eye and fish eye.
Lightest portions of a photograph or halftone, as compared to midtones and shadows.
Abbreviation for International Colour Consortium, an organisation which was established in 1993 to create, promote and encourage the standardisation and evolution of an open, vendor-neutral, cross-platform colour management system architecture and components. To do so, they developed the ICC profile specification
That portion of a printing plate that carries ink and prints on paper.
The correct sequential arrangement of pages that are to be printed, along with all the margins in proper alignment, before producing the plates for printing.
The pressure of a printing surface as it contacts paper.
A term to describe components of a system that are arranged in a logical production sequence. For example, an in-line film processor can be connected to an imagesetter so that the film is output directly from the imagesetter to the processor without operator intervention. Another example is in-line finishing equipment, which is connected directly to the printing press.
Ink Dry Back
When printed ink colours become lighter or less dense after they have dried on the paper.
Printed pages loosely inserted in a publication.
A coated stock finished in mother-of-pearl.
Abbreviation for International Standard Book Number, a reference number used to identify commercial books. It can usually be found on the back of the title page.
Text that is used to denote emphasis by slanting the type body forward.
The protective paper cover of a hardbound book. It is sometimes called a ‘dust cover’ or ‘dust jacket’.
To vibrate a stack of finished pages so that they are tightly aligned for final trimming or binding.
Abbreviation for Joint Photographic Experts Group, a compression algorithm named after the committee that defined it. Perhaps the best format for saving quality images in.
Adjusting the spacing or hyphenation of words and characters to fill a given line of text from end to end. Sometimes referred to as word spacing.
Abbreviation for black in four-colour process printing, comes from the word key, because black is the key colour used as a reference to achieve perfect registration. Hence the 'K' in CMYK.
The narrowing of space between two letters so that they become closer and take up less space on the page. Typical examples of combinations that require subtle kerning are an ‘r’ following a ‘T’ (the ‘r’ has to nestle underneath the right-hand bar slightly) or an ‘LY’ pair that have to nudge closer together. You can control kerning manually, or you can turn on the kerning built into a font by the font designer.
(1) Lines that are drawn on artwork that indicate the exact placement, shape and size of elements including halftones, illustrations etc.
(2) The border you put around a picture.
Kiss Die Cut
To die cut the top layer, but not the backing layer, of self-adhesive paper. Also called face cut.
Lightest possible impression that will transfer ink to a Substrate.
A shape of an object (e.g. a box, shape, text or a logo) that is printed by eliminating or removing (knocking out) all background colours or objects that it covers. The opposite of overprint.
Strong paper used for wrapping and to make grocery bags and large envelopes.
A parallel lined paper that has a handmade look.
A thin transparent plastic sheet (coating) applied to usually a thick stock (covers, post cards, etc.) providing protection against liquid and heavy use, and usually accents existing colour, providing a glossy (or lens) effect. Also known as cello glazing.
A document layout where the width is greater than the height. (the opposite of Portrait)
Register where ink colours overlap slightly, as compared to butt register.
Bond paper made especially smooth and dry to run well through laser printers.
Edge of a sheet of paper being fed into a printing press.
Lay Flat Bind
Method of perfect binding that allows a publication to lie fully open. (Also known as Lay Flat Perfect Binding.)
Space between lines of type. The distance in points between one baseline and the next.
One sheet of paper in a publication. Each side of a leaf is one page.
A single glyph (character shape) designed to be used in place of a particular sequence of two (or more) glyphs. The most common, used in most fine typography, are the so-called ‘f-ligatures’: fi, fl, ff, ffi and ffl.
In printing lightfastness refers to the rate at which inks change colour or get lighter as a result of being exposed to daylight, UV light, heat and acids or alkalis.
A paper that emulates the look and texture of linen cloth.
Paper whose fibres run parallel to the long dimension of the sheet. Also called long grain paper and narrow web paper.
One of the four process colours, or CMYK, the M is for magenta. Magenta is a predominately red colour with some blue. Magenta, cyan and yellow are also the three subtractive primary colours.
Paper that is used in the press set-up process before the printing run actually starts. Or the process of setting up press or bindery equipment to produce a specific product, including setting paper size, ink density, image alignment, fold sizes, etc., in preparation for the actual production run.
Flat (not glossy) finish on photographic paper or coated printing paper.
Ink that looks metallic when printed. Made with powdered metal or pigments that look metallic. The most common colours used are gold and silver.
In a photograph or illustration, tones created by dots between 30 percent and 70 percent of coverage, as compared to highlights and shadows.
A reproduction of the original printed matter and possibly containing instructions or direction.
Undesirable pattern resulting when halftones and screen tints are made with improperly aligned screens, or when a pattern in a photo, such as a plaid, interfaces with a halftone dot pattern
Spotty, uneven ink absorption. Also called sinkage. A mottled image may be called mealy.
No-carbon-required. Paper coated with chemicals that enable transfer of images from one sheet to another with pressure from writing or typing, without the need for a carbon insert. Also known as carbonless paper.
A light, low-cost unbleached paper made especially for newspaper printing.
Printing technique that transfers ink from a plate to a blanket to paper instead of directly from plate to paper.
(1) Characteristic of paper or other substrate that prevents printing on one side from showing through the other side.
(2) Characteristic of ink that prevents the substrate from showing through.
A font that consists of mathematical equations that describe what each letter shape (glyph) should look like. Outline fonts can be printed at any size and at any resolution without “jaggies” or loss of quality. TrueType fonts are typical examples of outline fonts.
(1)To print one image over a sheet previously printed with an image or colour.
(2) A shape of an object (e.g. box, shape, text or a logo) that is printed on top of background colours or objects that it covers. The opposite of knockout.
The total number of pages in a book, magazine or publication. Sometimes referred to as the extent.
The numbering of individual pages in a multi-page document
A hard finished paper that emulates animal skin used for documents, such as awards, that require writing by hand.
A binding process where the signatures of a book are held together by a flexible adhesive.
A printing press that prints on both sides of a sheet in a single pass through the press.
Punching small holes or slits in a sheet of paper or cardboard to facilitate tearing along a desired line.
An occurrence in printing whereby the tack of ink pulls fibres or coating off the paper surface, leaving spots on the printed surface.
The particles that give ink its specific colour by absorbing and reflecting certain light frequencies.
Abbreviation for Picture Element, the smallest discrete element of an image or picture on a computer screen; the smallest image-forming unit of a video display; a single element of a raster image.
Plastic spiral binding is a new alternative to wire binding, with the benefits being that it is strong and durable - yet flexible and lightweight. Pages are much less likely to pull apart and the coil will not bend or distort during delivery. Bound books lay flat when opened, and can fold back a full 360 degrees. Available in a wide range of colours.
The abbreviation of the Pantone Colour Matching System.
A document layout in which the height is greater than the width. (the opposite of Landscape)
A tradename of Adobe Systems, Inc. for its page description language. This language translates a digital file from an application into a language a compatible printer or other device can use to create its output.
The practice of inspecting incoming or outgoing jobs (ads, pages or complete flats) before trying to process or send them.
When a client visits a printing company to view actual printed sheets of their project before a full production press run is started.
To read and check for errors in artwork composition, typography, spelling, grammer and layout positioning.
A QR or Quick Response code is a two-dimensional barcode. Originally this technology was created for tracking parts in manufacturing processes. Nowadays it is also used for adding web links to a printed page. When you scan such a QR barcode using a webcam or mobile phone camera, the QR reader application takes you to a Web site, a YouTube video or some other web content. QR codes are an easy way of sending people to a site without having to type a URL (web address).
Any substance that softens and reduces the tack of ink.
The arrangement of two or more printed images in exact alignment with each other.
A cross-hair target outside the page or image area that is used to help align film separations or to align the printed images on the press sheet. The mark should appear on all separations.
Type, graphic or illustration reproduced by printing ink around its outline, thus allowing the underlying colour or paper to show through and form the image. The image 'reverses out' of the ink colour. Also called knockout and liftout.
The colour space of Red, Green and Blue. These are the primary colours of light, which computers use to display images on your screen. An RGB computer file must be translated into the CMYK (the primary colours of pigment) colour space in order to be printed on a printing press.
Using multiple ink colours in addition to black to produce a deep, dark black colour. Common CMYK values used are 40% Cyan, 0% Magenta, 0% Yellow and 100% Black.
The binding of booklets or other printed materials by stapling the pages on the folded spine.
A typeface that has no serifs (small strokes at the end of the main stroke of the character).
Alternate term for a smooth, but non-glossy finish on coated paper.
To crease paper with a metal rule for the purpose of making folding easier.
The placement of halftone screens to avoid unwanted moiré patterns. Frequently used angles are black 45º, magenta 75º, yellow 90º, and cyan 105º.
A measurement equaling the number of lines or dots per inch on a halftone screen.
Unwanted deposits of ink in the non-image area of a printed piece.
A cover that is the same paper stock as the internal sheets.
Thin lines added to the end of a letterform’s stem and stroke.
A printing problem that occurs when wet ink from the printed side of the sheet transfers to the back of the sheet above it.
To decrease the dot size of a halftone, which in turn decreases the colour strength.
Paper whose fibres run parallel to the short dimension of the sheet. Also called short grain paper and wide web paper.
When the printing on one side of a sheet is seen from the other side, a frequent problem with thin papers.
The stapling of sheets or signatures on the side closest to the spine.
A printed sheet with multiple pages on it that is folded so that the pages are in their proper numbered sequence, as in a book.
Separate sheets (stock) independent from the original run positioned between the "printed run" for a variety of reasons.
Inks made with soy oils instead of petroleum as the base. They are considered to be more environmentally friendly, a standard component of green printing.
A type of binding where a metal or plastic wire is spiralled through holes drilled along the binding side of a document.
Paper that, due to mistakes or accidents, must be thrown away instead of delivered printed to the customer, as compared to waste. Also known as overs.
A term for unprinted paper.
In typography, characters set in a smaller point size and positioned below the baseline. Subscript is typically used in chemical equations and sometimes called inferiors.
Type that is slightly smaller than the rest of the font and set above the baseline. Superscript is used for footnote markers and sometimes as the numerator of fractions. Also called superior characters.
Abbreviation for Scalable Vector Graphics: a fairly new file format that can be used to publish vector based drawings and animations on the world wide web. SVG has been defined by the W3C organisation so it is a vendor independent standard, as opposed to the competing and popular Macromedia Flash file format. SVG is based on XML tags and is only supported by the latest generations of browsers.
Any non-wood or cloth paper, usually petroleum (plastic) based.
Abbreviation for Total Area Coverage: the total build-up of ink on a given spot on the paper. An area where 70 percent cyan is combined with 50 percent yellow and 20 percent black has a TAC of 140.
The ‘stickiness’ or adhesive quality of ink while printing.
A type of cutting device used to trim three sides of a bound book simultaneously. This machine is typically used at the end of a binding or finishing line. A three knife trimmer is similar to a guillotine cutter but uses three knives instead of one, two parallel knives and one right-angle knife.
Abbreviation for Tagged Image File Format, a file format used for bitmap images.
A halftone screen that contains all the same sized dots, or a diluted variation of a full strength colour.
Powder or liquid ink used to print. Toner is used in laser printers as well as a lot of digital presses.
Decreasing or increasing the amount of space between letters in a word or a line of text.
The overlapping of one colour over a different, adjacent colour to ensure that no white space is visible where the two colours meet, especially when there are slight variations in the registration of the two colours during the printing process. Or the process of printing wet ink over wet or dry previously printed ink.
Marks placed on the printed sheet to indicate where cuts should be made.
The final size of a printed piece after being cut from the sheet of paper that it was printed on.
A spelling mistake in printed material resulting from a mistake in typing or setting type.
Paper that has not been coated with clay. Also called offset paper.
Technique of adjusting dot size to make a halftone or separation appear sharper (in better focus) than the original photo or the first proof. Also called edge enhancement and peaking.
A glossy liquid coating that is applied to a printed sheet or part of a page, then bonded and cured with ultraviolet light.
Abbreviation for UltraViolet ink, a special ink that dries quickly through the use of ultraviolet light on the press. This allows for more productivity because there is no need to let the ink dry before printing the other side. The inks are aggressive and will shorten the lifespan of the plates used.
The resistance to the fading of colours under direct sunlight
Is a form of on-demand printing in which elements (such as text, graphics, photographs, etc) can be changed from one printed piece to the next, without stopping or slowing down the press, using information from a database. For example, a set of personalizsed letters, each with the same basic layout, can be printed with a different name and address on each letter.
Liquid applied as a coating for protection and appearance. Gloss, satin and matt finishes available.
A file created on a page makeup system containing page design commands that specify the start, the end, and the length of each line. A vector file might also specify geometric shapes and their dimensions, e.g. a circle is defined by three pieces of discrete data, the circle centre point x, y location and the circle radius.
A fairly even uncoated and creamy paper finish.
A photo or illustration, in which the tones fade gradually away until they blend with the background they are printed on.
To clean ink and fountain solutions from rollers, fountains, screens, and other press components.
Unusable paper or paper damage during normal makeready, printing or binding operations, as compared to spoilage.
A translucent mark or image that is embossed during the paper making process, or printed onto paper, which is visible when the paper is held up to the light.
A single word or two left at the end of a paragraph, or a part of a sentence ending a paragraph, which loops over to the next page and stands alone. Also, the last sentence of a paragraph, which contains only one or two short words.
A layout in which both sides of a sheet can be printed using a single plate. The paper is flopped after the first side is printed so that the trailing edge of the first printing becomes the gripper edge for the second printing. The same side guide is used for both passes.
A layout in which both sides of a sheet can be printed using a single plate. The paper is turned over after the first side is printed, using the same edge of the first printing as the gripper edge for the second printing. Different side guides are used for each pass.
A smooth paper with a gentle patterned finish.
Abbreviation for eXtensible Markup Language, a subset of SGML constituting a particular text markup language for interchange of structured data.
One of the four process colours of ink, or CMYK. The Y is for yellow.
Binding term for two or more parallel folds that open like an accordion or concertina door, sometimes referred to as an accordion or concertina fold. Leaflets and maps often use these folds.