Envelope Glossary

Absorption: Absorption is the ability of paper to take up liquids or vapors. This plays a key role in the quality of the bonding process of the adhesives used to manufacture an envelope and in the storage process as the stored envelopes are subjected to humidity.

Adhesives: There are two main groups of adhesives used to manufacture an envelope. The first group consists of fastening agents used to bind the seams of the envelope together permanently. The second group includes the various sealing agents used to bind the seal to the backside of the envelope.

Air Mail Envelope: A lightweight envelope with red and blue border and “Air Mail” printed on the face, specifically designed for keeping the cost of postage down by reducing the weight of the mailing.

A-Style Envelope: Announcement style, open side envelope with double side seam construction and a square flap. Available in six standard sizes and most often converted from text paper.

Back Gum: Also called seam gum. It is the adhesive used to seal the seams on the back of the envelope to form the envelope pocket.

Bankers Flap Envelope: Also known as a wallet flap, this envelope is readily available in the larger commercial envelope sizes and is used for heavy mailing applications, such as bank statements that must get through the mail system intact and secure.

Baronial: Often used for announcements and greeting cards, this envelope has a large pointed flap and diagonal seams, and is available in five popular sizes. Companion panel and plain cards and folders are readily available in the standard sizes.

Basis Weight: The weight of 500 sheets of a standard size paper of a given grade. For example, 500 sheets of a 25 x 38 Basis 80 text paper weigh 80 pounds. In another example, 500 sheets of 17 x 22 Substance 24 bond or writing paper weigh 24 pounds.

Blank: The die cut paper in the form of an envelope prior to folding.

Bleed: When the printed image extends beyond the fold of an envelope or off the edge of a page or an envelope blank.

Blocking: The premature activation of the front seal gum in areas other than those directly above the back seam gum.

Booklet: An open side, double side seam envelope, usually having a wallet style flap. This envelope comes in many standard sizes. The most popular size is 9″ x 12″.

Bottom Flap: The section of the envelope folded up from the bottom score to form that portion of the back of an envelope.

Bang Tail: A booklet style envelope with an extension on the bottom flap that is “perfed” at the throat. This extension, or tail, is usually printed as an order form. Band Tail envelopes are commonly used by mail order companies and as credit card statement remittance envelopes.

Catalog Envelope: An open end center seam envelope with the seal flap on the short dimension. Catalog envelopes with a single side seam are not commonly used, but are available upon special order.

Center Seam: Most common on open end envelopes this is the permanent seam that joins the tow side flaps together at the center of the envelope, running form the bottom of the envelope to the throat of the envelope.

Clasp Envelope: Almost always made form an open end envelope, a clasp is secured to the back side of the envelope with a small reinforced hole punched in the flap for the clasp to slip through and be secured, The flap is usually gummed. The clasp can be used for added security if the seal is activated, or can be used repeatedly if the gum stays inactive.

Closures: Various methods of securing the seal flap to the back of the envelope.

  • String-And-Button: A string is affixed to the outside of the seal flap that the user winds around a disc that is affixed to the back of the envelope directly below the flap. Most commonly used on an inter-office envelope.
  • Latex: A self-sealing adhesive that requires no moisture. Latex gum is applied to the seal flap and to the back flap where the seal flap touches when closed. When the two latex gummed surfaces are pressed together, a bond is formed, holding the seal flap to the body of the envelope.
  • Remoistenable Seal Gum: Commonly referred to as regular gum. Required moistening to achieve a seal. There are two main types of seal gum. They are dextrine, a natural vegetable bi-product, and resin, a synthetic substance. Most remoistenable gum used today is a mixture of the two types.
  • Metal Clasp: A winged metal device that is affixed to the back of the envelope just below the throat and behind the seal flap. It is bent open by the user, inserted though a reinforced hole the seal flap, and bent back down to temporarily close the envelope.
  • Peel & Stick Flap Closure: This closure consists of a “super sticky” gum line applied to the seal flap this is covered by a strip of release paper. The extremely aggressive nature of this adhesive creates a very secure closure.
  • Tac-N-Tac: A re-sealable closure consisting of a clear vinyl tape affixed over a hole punched into the seal flap. Another piece of release tape is affixed to the back of the envelope below the throat and behind the flap. When the seal flap is closed, the tape exposed through the hole and the seal flap adheres itself to the release tape on the back of the envelope. This closure can be sealed and re-sealed many times. It is used as an alternative to the button and string closure on inter-office type envelopes.


Cello: Super clear cellophane window patch material. More costly than poly.

Coin Envelope: A small open end envelope ranging in size from #00 – 11/16″ x 2 ¾” to a #7 – 3 ½” x 6 ½”.

Commercial Style: Open side, diagonal or double side seam envelope with a commercial style flap. The most popular envelope for business, it is sometimes referred to as an “official” envelope. It is readily available in many paper varieties and comes in 11 common sizes, with or without a window.

Commodity Envelope: Envelopes usually mass-produced in standard sizes from open line papers, such as white wove and Brown Kraft. They are available for all customers of record to purchase.

Converting Only: Paper is supplied by the customer for conversion into envelopes.

Coupon Hitch-Hiker: A remittance envelope with a perforated coupon extending from the flap, and a perforated tail extending from the back flap.

Diagonal Seam: A seam running diagonally from the bottom fold and comes upward toward the throat of the envelope.

Die: In envelope making, this term usually refers to a high die for cutting envelope blanks or a window die for cutting a window opening.

Die-Cut: A process of cutting envelope blanks utilizing a high die.

Document Envelope: Sometimes referred to as legal envelopes, these are large, open side, double side seam outside, hex flap envelopes produced from heavy manila or brown kraft stock with heavy seal gum, used for mailing and storage of documents requiring security and confidentiality.


Expansion Envelope: Much like a grocery bag. The gussets in an expansion envelope allow it to be expanded to accommodate such things as book, binders, manuscripts, and countless other bulky items. They are made in both open end and open side styles, most commonly of 40 lb. Kraft paper.

Expansion Score: An additional score on a seal flap, running its length in order to accommodate bulk contents.

File-Velope: A large, open side envelope, without a flap, which has inside side seams and a short tab at its opening. Generally used as a file pocket.

First Class Mailer: Any type or size of envelope with a pre-printed diamond shaped border around its perimeter. A break in the border is left in the upper right hand corner on the face of the envelope to accommodate postage and eliminate interference of postal scanners. The words “FIRST CLASS” are normally pre-printed on the face and seal flap, but are not required. The most common color used in printing is green, but most any color can be used.

Flaps Extended: A term used to describe a request to have envelopes produced and packed with their flaps open and extended.

Flush Cut: The seal flap is removed, leaving a straight opening at the top of the envelope.

Foil Lined: The inside of the flap and throat are lined with a decorative foil. Used most often in greeting cards.

Fold: Any folded edge of the envelope. Generally referred to as the side, top or bottom fold.

Gum: Any type of adhesive or glue used in the manufacturing of envelopes.

Gum Sling: A term used to describe a manufacturing problem caused by back gum applications splattering gum onto other surfaces of the envelope resulting in consecutive envelopes tacking and sticking together.

Gum Seepage: A term used to describe a manufacturing problem caused by an excessive application of back gum resulting in consecutive envelopes sticking together at the seam or the inside pocket of the envelope being stuck closed at the seam(s).

Hitch-Hiker Envelope: A dual-purpose envelope for use in both outbound and return response mailing.

Indicia: Mailing permits that are printed on an envelope where a stamp would normally be placed.

Inter-Office Envelope: Usually an open end or catalog style envelope which is preprinted on both sides with lined depicting the person(s) and department that the envelope is to be delivered to. On a standard 10″ x 13″ size there are enough spaces to accommodate 56 deliveries. Eight 3/8″ holes are drilled completely through the envelope for visible confirmation of any contents. Button and string or Tac-N-Tac closures are used on this type of envelope.

Job Jacket Envelope: A large envelope in which all aspects of a print job are kept for reference.

Jumbo Envelope: A very large envelope of either open end or open side construction. Ranging in size from 9″ x 16″ to 24″ x 36″ which can be machine folded to even larger sizes, which must be hand folded. Most super size envelopes are constructed of 28 lb. to 40lb. Kraft paper.

Open End: An envelope term describing an envelope with the seal flap on the shorter of the two dimensions.

Open Panel: A term used when any envelope with a window does not have any type of clear window patch material affixed over the window opening from inside the envelope.

Open Side: An envelope term describing an envelope with the seal flap on the longer of the two dimensions.

Policy Envelope: An open end style envelope with the same dimensions as a #10 through a #14 commercial envelope.

Poly: Polyclear window patch material, the most common window patch material.

Proxy Envelope: A booklet style envelope with either an inside pocket affixed on three sides behind a window, or one with separate commercial type envelope affixed to the outside. The proxy envelope is used to mail annual reports along with proxy voting cards to corporate stockholders.

Regular: A term used to describe any commercial envelope that does not have a window.

Remittance Envelopes: A booklet or side seam style envelope with a long wallet type seal flap covering most of the back of the envelope. Used as a collection envelope. Most common sizes being of the commercial and official sizes #6 ¼, #6 ¾, and #9. Boxed with flaps extended.

Safety Fold Envelope: An open side, center seam envelope with a large wallet flap and a high throat designed to fold over with the flap to increase the security of the contents.

Seal Gum: Any adhesive applied to the seal flap of the envelope in order to achieve a seal. See closures.

Seal Flap: The flap that folds down over the envelopes opening in order to seal it.

Shoulder: The top edge of the side flaps at the envelope opening.

Side Flaps: Fold in from the sides to form the sides of the envelope.

Side Seam: A seam that runs perpendicular to the envelope opening.

Side Seam Inside: The term applied to the side seam when it folds UNDER the bottom flap.

Side Seam Outside: The term applied to the side seam when it folds OVER the bottom flap.

Special: A very general term used to describe any envelope that is not of a standard size, window position, or paper grade.

Straight Grain Cutting: Cutting the blanks for an envelope so the grain of the paper runs parallel to the folds.

Tabbed: A counting method for packed envelopes, which places a paper tab at specified quantities within the box or carton to assist the printer or inserter to select the correct amount of envelopes needed for the operation being performed.

Tacking: The premature activation of the seal gum at the points where it is over the back seams of an envelope.

Throat: The opening at the top of the envelope. The size of the throat is measured form the top edge of the bottom flap to the fold line of the seal flap.

Thumb Cut: A rounded opening cut through the back, front, or both sides of an envelope opening to facilitate the removal of its contents.

Tyvek: A synthetic paper made by the DuPont. It is an ultra-lightweight, tear-proof, and waterproof “paper” which when converted into envelopes can accommodate heavy, bulky, and highly confidential mailings. Although Tyvek has countless uses, 14 lb. and 20 lb. stock is used for envelope converting.

Wallet Flap: A type of seal flap that is deep and square in shape.

Web Cut: Any envelope manufactured by means of feeding a continuous roll of paper into and envelope machine, which cuts the envelope blanks individually with inline rotary knives. The most common web-cut envelope style is of side seam construction.

Window: An opening in the envelope with or without a translucent patch designed to allow the contents inside the envelope to show through.