Packaging Terminology Glossary

Custom packaging has its own vocabulary, and most of it is assumed rather than explained. This glossary defines the terms you are likely to meet when specifying, quoting or approving printed packaging in the UK, grouped by the stage of the job they belong to. Where a term has its own guide or page, the definition links to it.

This guide is general information, not legal or compliance advice. The regulatory terms near the end describe how the rules work in outline; always check the current official guidance for your own packaging.

UK packaging uses millimetres for dimensions, gsm and microns for carton board, flute letters for corrugated board and millimetres for greyboard. If you are new to custom packaging, start with our complete guide to custom packaging in the UK.

Board and paper

Board

Paper made thick and stiff enough to form a box, sometimes called paperboard or carton board. Folding cartons use board of typically 250–400 gsm; rigid boxes use much thicker greyboard. See our packaging materials guide.

Folding boxboard (FBB)

A layered carton board with a bulky mechanical-pulp core between bleached outer layers. It is stiff for its weight, prints well on its coated face and is the everyday board for printed folding cartons. See folding boxboard and SBS.

Solid bleached board (SBS)

Carton board made from bleached chemical pulp all the way through, so the face, back, edges and creases are all bright white. It gives the finest print and crispest foil, and is chosen for cosmetics, fragrance and premium cartons.

GC1 and GC2

Grades of folding boxboard. GC2 has a cream or manila back and is the most common carton grade; GC1 has a whiter back for cartons that are seen open or printed inside.

White-lined chipboard (WLC)

Carton board made largely from recycled fibre, with a white coated printing face and a grey back. It is an economical choice for cartons and inner packs where the back is not seen.

Coated board

Board with a thin mineral coating on the printing face, giving a smooth, even surface for sharp print and consistent colour. Uncoated board has no such layer, so ink sinks in further and colours print softer and slightly darker. See coated vs uncoated board.

Kraft board

Unbleached board made from kraft pulp, keeping its natural brown colour and long, strong fibres. It takes bold one- and two-colour printing well and suits natural-look cartons, mailers and sleeves. White-top kraft adds a white printing face over a brown back. See kraft board.

Greyboard (chipboard)

Thick, dense, unlined board, usually made from recycled fibre and typically 1.5–3 mm thick, used as the structural core of a rigid box. It is wrapped in printed paper rather than printed directly. See greyboard.

Wrap paper

The printed or speciality paper glued over the greyboard of a rigid box and turned in over its edges. Printed wraps are commonly 120–157 gsm art paper, laminated before wrapping so the corners resist scuffing.

Lining paper

The paper that covers the inside of a rigid box's lid and base, hiding the turn-ins of the wrap. It can be plain, coloured or printed to carry a pattern or message.

Speciality papers

Textured, linen-finish, coloured, pearlescent or metallic papers used as rigid box wraps and premium sleeves. They are often left unprinted and decorated with foil blocking or debossing instead. See speciality papers.

GSM (grams per square metre)

The weight of one square metre of board or paper, and the standard measure of carton board weight in the UK. Higher GSM generally means stiffer board, but GSM describes weight, not thickness. See GSM and board thickness explained.

Calliper

The physical thickness of a board, measured in microns (thousandths of a millimetre, written µm). Two boards of the same GSM can have different callipers: folding boxboard is thicker than SBS at the same weight because its core is bulkier.

Points

A unit of board thickness used in the United States. UK suppliers specify carton board by GSM and calliper in microns instead, so a US specification in points needs converting before it can be quoted.

Grain direction

The direction in which most fibres lie in a sheet of board. Board folds more cleanly and stays flatter when the main creases run with the grain, so blanks are laid out on the sheet with grain direction in mind.

Corrugated board and flutes

Corrugated board

Board made from a wavy fluted paper layer glued between flat paper liners. The flutes give cushioning and stacking strength for its weight, which is why corrugated is used for mailer boxes, transit boxes and displays. See corrugated board.

Flute

The wave-shaped inner layer of corrugated board, also called the fluting or medium. Flutes are graded by letter according to their height: finer flutes give a smoother print surface, taller flutes more cushioning and stacking strength. See E vs B vs C flute.

Liner

The flat paper layers either side of the flute. Kraft liners are made mainly from virgin fibre and are strongest; test liners are made from recycled fibre; white-top liners have a white surface for brighter full-colour print.

Single wall

Corrugated board with one fluted layer between two liners. It covers most mailer boxes and postal boxes, in E, B or C flute.

Double wall

Corrugated board with two fluted layers and three liners, such as EB or BC double wall, typically about 4–7 mm thick. It is used for heavy, fragile or stacked loads and floor-standing displays.

E flute

A fine flute about 1.5 mm thick with a smooth surface that takes detailed print well. It is the usual board for printed mailer boxes, product boxes and counter display units.

B flute

A flute about 3 mm thick, with more cushioning and crush resistance than E flute. It is the general-purpose single wall for postal and transit boxes and heavier e-commerce orders.

C flute

A taller flute about 4 mm thick, with good cushioning and stacking strength. It is common for transit boxes and heavier contents, and prints less finely than E or B flute.

F flute (micro flute)

A very fine flute, roughly 1 mm thick or less, used where a box needs to be slimmer than E flute but stiffer than carton board.

Washboarding

Visible ribbing on printed corrugated board where the flutes show through the liner. It is most noticeable on taller flutes and large flat areas of colour; finer flutes and litho-laminating reduce it.

Edge crush test (ECT)

A laboratory measure of the load corrugated board can take on its edge before it crushes, used to predict how well a box will stack. Bursting strength is an older measure of resistance to pressure across the face of the board.

Litho-laminating

Printing a paper liner by litho and then laminating it onto fluted board to make a printed corrugated sheet. It gives the sharpest full-colour print on corrugated and is used for premium mailer boxes and displays.

Box types and styles

Folding carton

A printed board box supplied flat, with its side seam glued, and folded into shape at the point of packing. The most common form of retail packaging. See printed folding cartons.

Rigid box (set-up box)

A box built from thick greyboard and wrapped in printed paper. It arrives already assembled and holds its shape permanently, and is used where perceived value matters. See custom rigid boxes.

Mailer box

A die-cut corrugated box with a fold-over lid and tuck-in front that closes without tape, used where the same box ships the order and presents it on opening. Postal box usually means the same thing. See mailer boxes.

Regular slotted carton (RSC)

The standard corrugated transit box, with four flaps at the top and bottom that meet in the middle and are taped shut. It suits bulk and trade shipments where presentation matters less. See printed corrugated boxes.

FEFCO code

A four-digit number from the European corrugated industry's catalogue of standard box designs. For example, FEFCO 0201 is the regular slotted carton and FEFCO 0427 is the familiar roll-end tuck front mailer.

Straight tuck end (STE)

A folding carton with a tuck closure at each end, both hinged from the same panel, so the carton opens cleanly at the front. See straight tuck end boxes.

Reverse tuck end (RTE)

A folding carton whose two tuck closures hinge from opposite panels. The blanks nest more tightly on the sheet, which uses less board, but the top tuck opens from the back. See reverse tuck end boxes and straight vs reverse tuck end.

Crash-lock (auto lock) bottom

A carton base that is partly glued during manufacture and locks into a flat floor as soon as the carton is squared open, with no hand folding. It carries more weight than a tuck and speeds up packing. See crash-lock bottom boxes.

Snap lock (1-2-3) bottom

A carton base of four interlocking flaps folded in sequence by hand. It is stronger than a tuck bottom and needs no base gluing, but is slower to pack than a crash-lock. See snap lock bottom boxes and crash lock vs snap lock.

Seal end carton

A folding carton whose end flaps are glued shut rather than tucked, used for machine-filled products and where tamper evidence matters. See seal end boxes.

Roll-end tuck front (RETF)

The standard one-piece mailer construction: side walls roll over and lock with tabs, dust flaps close the corners and the front of the lid tucks into the base. See roll-end tuck front mailer boxes.

Lid and base (two-piece)

A box made of two parts, a base and a separate lid that lifts off, in rigid board or corrugated. See lid and base boxes and corrugated lid and base boxes.

Magnetic closure box

A rigid box with a hinged, wrap-around lid that opens like a book and is held shut by magnets concealed under the wrap. See magnetic closure boxes.

Book-style box

A rigid box with a hinged cover that opens like a book, closing by magnets, ribbon or simply by the fit of the cover. See book-style boxes.

Drawer box (slide box)

A tray that slides out of an open-ended sleeve, often with a ribbon or thumb cut to pull it. Made in rigid board or carton board. See drawer boxes.

Shoulder and neck box

A rigid box with an inner neck that rises above the base. The lid closes down onto the shoulder so lid and base sit flush, and the neck is revealed as the lid lifts. See shoulder and neck boxes.

Collapsible rigid box

A rigid box that ships flat and folds into shape, usually held by magnets or ribbon. It combines rigid-box presentation with lower storage and delivery volume. See collapsible rigid boxes.

Sleeve

An open-ended printed band that slides over a box, tray or product. It carries branding while the inner box stays plain, and lets one inner box serve several variants; a slipcase is a rigid version. See sleeve and slipcase boxes.

Pillow box

A curved carton with rolled, closing ends, resembling a pillow, used for small, light retail items and gifts. See pillow boxes.

Gable box

A carton with a peaked top and an integral carry handle, used for gifting, events and food to go. See gable and handle boxes.

Window box

A carton with a die-cut opening, usually backed with a clear film patch, so the product can be seen without opening the pack. See window boxes.

Counter display unit (CDU)

A printed box, usually in E flute or heavy board, that holds products on a shop counter, often with a raised header card carrying the branding. See counter display units.

Shelf-ready packaging (SRP)

An outer case designed to go straight onto a retail shelf, usually by tearing away a perforated front section to leave a tray of products facing the shopper.

Hang tab

A die-cut tab at the top of a carton, often with a Euro slot-shaped hole, that lets the pack hang on a retail peg.

Box parts and construction

Glue flap (manufacturer's joint)

The narrow flap along one edge of a carton blank that is glued to the opposite panel to form the side seam. It is kept free of heavy ink and lamination where the glue has to bond.

Dust flap

A small flap at the end of a carton or mailer that folds in under the tuck or lid, closing the gaps at the corners and stiffening the end.

Tuck flap

The flap on the end of a closure panel that tucks inside the carton to hold it shut.

Friction lock

Small slits or shaped nicks where a tuck flap meets its panel, which catch against the dust flaps and hold the tuck closed.

Crease (score)

A line pressed into the board so it folds cleanly and consistently in the right place. Creases are made by rounded rules in the cutting forme at the same time as the cuts.

Perforation

A line of small cuts that allows part of the box to be torn away cleanly, used for tear strips, dispensers and shelf-ready packaging.

Tear strip

A perforated or reinforced strip that opens a box cleanly and shows whether it has been opened before, common on mailer boxes.

Turn-in

The margin of wrap paper folded over the edges of a rigid box and glued to the inside, usually hidden by the lining paper. Even, well-glued turn-ins are one of the signs of a well-made rigid box.

Corner stay

A strip of paper or tape applied over the corners of a rigid box shell to hold the greyboard walls together before the wrap goes on.

V-grooving

Cutting a V-shaped channel into greyboard so it folds into a sharp, square corner. It is used on rigid boxes, especially lids and book-style covers, where crisp edges matter.

Inserts and interior components

Insert

A fitted component that holds the product in position inside the box. It is made from card, corrugated board, foam or moulded pulp depending on the weight, value and fragility of the contents. See custom box inserts.

Divider

An insert that separates several items within one box, such as bottles, jars or a set of products, so they cannot touch in transit. Also called a partition.

Foam insert

An insert cut from foam, commonly EVA, with cavities shaped to the product. It suits delicate or high-value items but adds a non-paper material to the pack.

Moulded pulp

Paper fibre formed into a shaped tray or cradle in a tool. It is a paper-based alternative to foam for holding heavier or awkwardly shaped products.

Void fill

Loose material, such as paper, used to fill the empty space around a product in an oversized box. A box sized to the product, with a fitted insert where needed, reduces or removes the need for it.

Dimensions and sizing

Internal dimensions

The space inside a box, written as length × width × depth in millimetres, with length and width describing the opening. Custom packaging is specified by internal dimensions because that is what has to fit the product. See how to measure a box.

External dimensions

The overall size of a box including the board, roughly the internal dimensions plus twice the board thickness on each side. External dimensions decide postal size bands, shelf fit and how many boxes go in an outer carton. See internal vs external dimensions.

Clearance

The small gap allowed between the product and the inside of the box so the product goes in without forcing and the closures lie flat. Too little and it will not fit; too much and it moves in transit.

Blank

The flat, cut and creased piece of board before it is folded and glued into a box. Blanks are laid out several to a press sheet where the size allows.

Right-sizing

Designing a box to fit the product closely, so it uses less board and void fill and takes less space in transit. See reducing excess packaging.

Printing and colour

Litho (offset lithography)

A printing method that transfers ink from metal plates via a rubber blanket onto the sheet. It gives fine detail and exact spot colours, and becomes economical at larger quantities once the plates are made. See litho vs digital printing.

Digital printing

Printing directly from the file with toner or inkjet, with no plates. It suits short runs, several versions and personalised designs.

Flexographic printing (flexo)

Printing with flexible relief plates, widely used to print directly onto corrugated board. It is typically used for simpler graphics, often one or two colours on kraft.

CMYK

Four-colour process printing with cyan, magenta, yellow and black inks, which combine to build full-colour images. It is the right choice for photographs and complex artwork. See CMYK vs Pantone.

Pantone (PMS)

The Pantone Matching System: a library of pre-mixed ink colours identified by reference numbers. It is used where a brand colour must reproduce consistently across a range and across reprints. See Pantone colour matching.

Spot colour

A single pre-mixed ink printed as its own colour rather than built from CMYK, usually specified as a Pantone reference. Metallic and fluorescent colours can only be printed as spot colours.

Rich black

Black built from black ink plus other process colours, which prints deeper than black ink alone on large areas. Small text is kept in black only, so slight movement on press cannot create coloured fringes.

Flood colour

A single colour printed across a whole panel or the whole box. Large solid areas show marks and colour variation more readily than images, so they are often protected with lamination.

White underlay

A layer of white ink printed beneath other colours on kraft, metallic or clear materials, so colours read brighter and white elements show at all. Without it, colours on kraft print darker and white cannot appear.

Registration

The accurate alignment of each printed colour with the others, and of print with foil, embossing, spot UV and cutting. Slight misregistration shows as colour fringes or finishes that sit off their artwork.

Make-ready

The setup work that brings a press or finishing machine to the right settings before a run, including reaching the correct colour and register. Sheets used during make-ready are waste, which is one reason setup is shared across the run.

Inside printing

Printing the inside faces of a box, usually on the reverse of the same sheet. It is often where the most memorable part of a mailer's design goes. See printing inside your box.

Artwork and pre-press

Dieline (cutter guide)

The flat template showing every cut, crease and fold of a box at its true size. Artwork is designed onto the dieline so that print elements land correctly once the box is folded. See what is a dieline?.

Pre-press

The checks and preparation between receiving artwork and printing it: checking files, fitting artwork to the dieline, setting up colours and laying out blanks on the sheet, known as imposition.

Bleed

Artwork extended beyond the cut line, usually by 3 mm, so that no unprinted edge appears after cutting. Artwork supplied without bleed risks white slivers along the box edges. See bleed, trim and safe areas.

Trim line

The line where the board is cut, also called the cut line. On a dieline it is usually shown as a solid line, with creases shown dashed.

Safe area

The zone inside the trim line, commonly 3–5 mm in from every cut and crease, where important text and logos should sit so they are not cut off or caught in a fold.

Vector artwork

Artwork built from mathematical paths rather than pixels, such as logos, type and line drawings. It scales to any size without losing sharpness and is the preferred format for logos and foil. See vector vs raster.

Raster image

An image made of pixels, such as a photograph. It prints well only if its resolution is high enough at the size it will be printed.

Resolution

The density of pixels in a raster image, expressed in ppi. Images for print generally need about 300 ppi at their printed size; web images are usually far lower and look soft or blocky on a box.

Print-ready PDF

A PDF, often to a PDF/X standard, with artwork on the dieline, colours in CMYK or named Pantone spot colours, fonts embedded or outlined, images at print resolution and bleed included. See preparing print-ready artwork.

Outlined fonts

Text converted into vector shapes so it prints correctly without the original font files. Once outlined, the text can no longer be edited, so keep an editable copy.

Overprint

Printing one colour on top of another without removing the colour underneath. Black text is often set to overprint so a small register shift cannot show a white gap; other colours usually knock out, meaning the colour beneath is removed.

Total ink coverage

The combined percentage of CMYK ink in the darkest part of an image. Board can only take so much ink before it smears or dries slowly, so print-ready files keep within the printer's limit, often around 300% for coated board.

Barcode

A machine-readable code, in UK retail usually an EAN-13 number issued through GS1 UK. On a box it needs enough size, a clear margin and dark bars on a light background to scan, and should not sit across a crease or glue area.

Proof

A representation of the job that you check and approve before production. Approval confirms the artwork, the size and the specification, and nothing is produced until it is given.

Digital proof

A PDF showing your artwork on the dieline, often with a 3D visual of the folded box. It shows layout and content accurately; colour on screen is a guide only, because screens and board render colour differently. See why screen colours differ from printed colours.

Physical sample

A made-up example of the box before the full run, either a plain structural sample to check fit or a printed sample. Ask about sample options when you request your quotation. See when is a physical sample needed?.

Finishes and embellishments

Lamination

A thin plastic film bonded over the printed surface, typically around 15–30 microns, protecting the print and setting the finish. Free Lamination is standard on every order. See lamination.

Matt lamination

A low-glare laminate that softens colour slightly and gives a calm, restrained surface. It is the most versatile finish and the best base for spot UV and foil.

Gloss lamination

A shiny laminate that makes colours brighter and more saturated and is easy to wipe clean, but shows glare under shop lights and fine scratches.

Soft-touch lamination

A matt laminate with a velvety, suede-like surface, used on premium cosmetic and gift packaging. It gives deep, muted colour but marks more easily with fingerprints and rubbing.

Aqueous (AQ) coating

A water-based protective coating applied across the printed sheet on or after the press. It gives lighter protection than lamination and adds no separate film layer.

UV varnish

A liquid coating cured instantly under ultraviolet light, applied across the whole sheet for a gloss, satin or matt surface.

Spot UV

A high-gloss UV coating applied to selected areas only, such as a logo, creating visual and tactile contrast against a matt or soft-touch background. See spot UV.

Foil blocking (hot foil stamping)

Applying a metallic, coloured or holographic foil to the board with a heated die and pressure. It is most often used on logos and typography. See foil blocking.

Embossing

Pressing the board between a matched pair of dies to raise part of the design above the surface. It works best on bold, simple shapes; with no ink or foil it is called a blind emboss. See embossing and debossing.

Debossing

The reverse of embossing: the design is pressed into the board rather than raised. It reads well on thick board and rigid box wraps.

Registered emboss

An emboss or deboss aligned exactly with printed artwork or foil, such as a foil logo that is also raised. It needs accurate registration between the processes.

Window patching

Gluing a clear film over a die-cut opening in a carton so the product is visible and protected. See window patching.

Production and conversion

Die-cutting

Cutting the printed sheet into box blanks with a cutting forme, creasing the fold lines at the same time. No Die Charges are standard on every order.

Cutting forme (die)

A board set with steel rules bent to the outline of the box: sharp rules cut and rounded rules crease. One is made for each box size and style.

Stripping

Removing the waste board from around and between the blanks after die-cutting, leaving clean, separate blanks.

Folder-gluer

The machine that folds a carton blank and glues its side seam, and on crash-lock styles its base, so it can be delivered flat and squared open at packing.

First-off check

Checking the first items from each machine against the approved proof and specification before the run continues, for example colour on press or base locking on the folder-gluer.

Overs and unders

The small difference that can arise between the quantity ordered and the quantity delivered, because a few sheets are lost in setup and finishing. How it is handled is agreed on the quotation.

Ordering, quoting and delivery

MOQ (minimum order quantity)

The smallest quantity that can be produced for one specification. Our minimum order is 50 boxes. See minimum order quantity explained.

Unit cost

The cost of each box at a given quantity. Because setup is shared across the run, unit cost falls as quantity rises, which is why quantity is one of the first questions on any quotation. See why unit cost falls at higher quantities.

Setup

The one-off work at the start of a job: pre-press, plates, make-ready and machine setting. It costs the same for a short run as a long one, which is why short runs have a higher unit cost.

Specification

The written description of exactly what is being bought: style, internal dimensions, board, print, finishes, inserts, quantity and delivery. See how to write a packaging specification.

Lead time

The time from order to delivery, which depends on the style, finishes, quantity and how quickly artwork and the proof are approved. Tell us your required delivery date and our team will confirm whether the timing is achievable. See custom packaging lead times.

Version

One design within an order, sometimes called an SKU. Each version needs its own artwork and proof, even when the box size and style are shared.

Reorder

A repeat of an approved specification. Reorders are simpler than first orders because the dieline and artwork already exist; any change means a new proof.

Delivered flat

Supplied unfolded to save storage and delivery space, then squared open or folded at packing. Folding cartons, mailers and collapsible rigid boxes are delivered flat; standard rigid boxes arrive assembled.

Outer carton

A plain corrugated box used to pack and deliver printed boxes or to ship several retail packs together, also called a shipper.

Size band

A carrier's grouping of parcels by external dimensions and weight, which sets the cost of sending them. A few millimetres of extra board can move a parcel into a higher band. See Royal Mail and courier size bands.

Sustainability and UK regulation

Recyclable

Capable of being collected, sorted and reprocessed into new material in practice, not just in theory. In the UK, what matters to most consumers is whether a pack is accepted in household (kerbside) collections. See recyclable packaging materials.

Recycled content

The proportion of a material made from recovered fibre or plastic. Recycled board suits many uses; virgin fibre, made directly from wood pulp, is stronger and brighter and is chosen where those matter. See recycled vs virgin fibre board.

Mono-material

Packaging made from a single material family, such as all paper and board, which is simpler to sort and recycle than a pack combining board, foam and plastic film.

Compostable

Packaging designed to break down in composting conditions. Industrial and home compostability are different standards, and compostable items generally should not go into paper recycling.

FSC

The Forest Stewardship Council, an international certification system for responsible forest management. A product can carry the FSC label only when each business in the supply chain that takes ownership of the material holds FSC chain-of-custody certification. See FSC certification explained.

PEFC

The Programme for the Endorsement of Forest Certification, another international forest certification system that also works through chain-of-custody certification.

Extended producer responsibility (EPR) for packaging

UK rules that make businesses supplying packaging responsible for data on, and in many cases the cost of managing, the packaging they place on the market. Whether and how it applies depends on a business's turnover and the amount of packaging it handles. See UK packaging EPR.

Plastic Packaging Tax

A UK tax, in force since 1 April 2022, on plastic packaging components made in or imported into the UK that do not contain enough recycled plastic. A component is classed by the material that makes up most of its weight, so paper-based packaging is generally outside it. See Plastic Packaging Tax.

OPRL

The UK's on-pack recycling labelling scheme. Its labels tell consumers whether a pack, or each part of it, can be recycled at home, and brands join the scheme to use them.

Food contact material

Any material intended to come into contact with food. Board for direct contact must be suitable for that use, so tell your supplier at the start if a box will touch unwrapped food. See food packaging.

Green claims

Environmental statements on packaging, such as "recyclable" or "made from recycled material". The Competition and Markets Authority's Green Claims Code expects them to be truthful, clear and backed by evidence. See sustainable packaging guide.

Terms that are often confused

For any term used in a quotation that is not defined here, ask when you request your quotation.