Envelopes are divided into two basic types
Pocket Envelopes seal on the shortest edge, Wallet Envelopes (also known as Bankers Envelopes) seal on the longest edge.
Size is always stated as Depth x Width. The width is always the seal-flap side and stated second. For example, 110 x 220mm denotes a wallet, whereas 220 x 110 denotes a pocket.
Each type has certain common terminology even if the shapes differ, such as seal-flap, seam etc. The back or reverse of an envelope is the side on which the seams are made. The other side is called the face.
Standard Envelope Sizes
Seal Flap Types
Gummed flap envelopes need to be moistened to seal down, and are used for hand sealing as well as on automatic inserting machines.
Self-seal envelopes have two lines of natural rubber latex, and seal on contact without the need for moistening.
Re-seal envelopes are similiar to self-seal envelopes but can be opened and resealed as necessary, ie for customs inspection etc.
Peel and seal flaps
Peel and seal envelopes have a single line of synthetic contact adhesive which is covered by a silicone release liner paper. Removal of the liner paper allows the flap to be sealed.