The seal flap is the portion of the envelope that is folded over and sealed to the rest of the envelope. Numerous styles are available to accommodate the functionality and appearance required.
Designed with semi-rounded ends, commercial flaps are designed to be processed quickly through mail metering machines. They also seal easily when bulky contents are being mailed and work well in most inserting and laser printing equipment.
Often used on Announcement style envelopes, square flaps have a contemporary look with a large imprint area. The lack of a shoulder area, however, can cause problems with automatic inserting equipment.
This flap is somewhat squared, but with rounded corners. It is most commonly used on booklet style envelopes and heavy mailing applications because it seals bulky contents well and can be used in most automatic inserting, mail metering, and printing equipment.
The most common form of flap for baronial style greeting card envelopes and stationary, this style does not tend to work well with inserting or metering equipment.