Construction Printing Knowledge

Construction Terminology | Window Types | Closure Types

Envelopes are constructed in many different ways. The envelope can vary in the type of paper, seams, closures, size and special features used. All envelopes are manufactured as a sheet and then folded according to the type of envelope being produced. Shown below are two standard envelope constructions. The diagrams will give you a basic idea of how most envelopes are constructed.

Construction Samples

Construction Terminology

Bangtail - The extra flap on the back panel of the envelope, which is detached at the perforation before the envelope is mailed.


Center Seam - A glued seam that runs up the middle on the back side of the envelope, from the bottom edge up to the throat.

Closure - The way in which an envelope is sealed at the opening.

Commercial - The most commonly used envelope style. It is an open side with diagonal seams. Available as a regular or a window envelope.

Diagonal Seam - Seams that run diagonally across the back of the envelope from the bottom corner to the throat. Used mostly in commercial, announcement, invitation and baronial envelopes.

Gusset - The expandable sides on an expansion envelope.

Inside Tint - Printing on the inside of the envelope that protects against seeing the contents of the envelope.

Open End/Catalog - The opening of the envelope is on the shorter side. An open end will generally have a center seam on the back.

Open Side/Booklet - The opening of the envelope is on the long side. An open side generally has diagonal seams or double side seams.

Inside Seams - A side seam that is glued under the back panel. Inside seams allow the entire back panel to be printed.

Outside Seam - A side seam that is glued on top of the back panel, limiting the printable area on the back panel.

Regular Envelope - An envelope that does not have a window cut out of it.

Seal Flap - The flap at the top of the envelope that folds down over the throat to seal the opening of the envelope.

Side Seam - A glued seam that runs parallel to the side fold, used to hold the envelope together.

Throat - The opening area on an envelope that generally gets covered by the flap when the envelope is sealed.

Thumb Cut - A half circle die cut out of the opening edge, either through one side or both. It is used on envelopes without flaps to make it easier to remove the content.


Top - The edge of the envelope where the opening is, whether it is on the short or long edge.

Window - A die cut opening in the body of the envelope, used to show a portion of the content of the envelope, such as, an address or a special message.

Window Types

A window is used on an envelope to allow a portion of the envelope content to be visible. There are standard size windows for different types of envelopes but most any size window can be added to any type of envelope. It is best to see if there is a standard window envelope that will fit your needs and then design your content to fit the window, this will save the additional cost of a custom window envelope. Also, when ordering a custom envelope, there may be a minimum order quantity required.

9 x 12 Catalog Envelope
with a Standard Window

#10 Window Envelope
with a Standard Window

#8 5/8 Double Window Envelope
with inside tint and two Standard Windows

Window Patch - Covering for the window opening.

Patch Types:
Polyclear - Most popular, least expensive, and best for scanning by postal service.
Glassine - Cloudier than polyclear, harder to achieve acceptable postal scanning . Is completely recyclable.
Cellophane - Higher clarity than polyclear but more expensive. Acceptable for postal scanning but is not recyclable.

Window Position - Location of the window from the left edge and up from the bottom.
See: Window Size and Placement.

Note: The window envelope does not have to have a patch covering the window. It can be left as an open window.

Closure Types

There are several different closure types available. Some of the standard envelopes are available with different types of closure. Adding a closure to an envelope, that is not a standard closure for that envelope, would require a custom order. Contact your supplier with any special requests you may have.

Shown below are some of the common types of closures available.

Remoistenable Gum - Most commonly used adhesive. It is applied to the seal flap and must be moistened to adhere the flap to the envelope.

Split Seal Gum -
The gum adhesive on the seal flap is broken where the flap covers the envelope seams, preventing flaps from sticking to the back panel when stored in humid conditions.

Latex Seal - A pressure sensitive adhesive that only sticks to itself. A strip is applied to the seal flap and the back panel. Envelopes are stored with flaps extended and will not stick until the flap is folded down and the adhesive on the flap and the back panel come in contact with each other.

Flip and Seal -
Available on open side envelopes with side seams. There are two flaps on the envelope, one in the standard position with a latex seal and a second one folded down at the throat of the back panel with the latex seal folded under. When the second flap is folded up and the seal flap is folded down, the two latex seals come in contact with each other and form the seal.


Peel & Seal -
The seal flap has pressure sensitive adhesive applied to it and there is a protective release paper covering the adhesive. The release paper is removed and when the flap is folded down and pressure is applied, the flap will adhere securely to the envelope.

Resealable -
An adhesive designed to form a lighter bond so that the envelope could be opened and closed multiple times without damaging the envelope.

Clasp -
A metal clasp is used in addition to a regular gummed flap. The clasp adds security to the closure and also allows repeated opening and closing of the envelope.

String and Button -
A manual closure where a string and button are attached to the flap and a button is attached to the body of the envelope. The string is wrapped around the button on the body and then the back up around the button on the flap to seal the envelope. Used on inter-office and reusable envelopes where repeated opening and closing of the envelope is necessary.


Tuck-in-Flaps - A type of closure that has two tabs on the flap. When the flap is folded down, the tabs fit into slots on the body of the envelope to form the seal. Tuck-in-Flaps are used on board mailers and provide a secure closure without the use of adhesive.

Tamper-Evident -
A security closure, available on various Tyvek® envelopes, that alerts the recipient if the envelope had been opened before they received it.
See: Envelope Types - Tyvek® Tamper Evident.


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