an envelope that opens on the short side.

Also called a pocket envelope, an open end envelope has its opening flap on one of the short sides, and usually has a center seam on the back or a side seam. Catalog envelopes have an open end.

The open end envelope has its opening on the shorter dimension and usually has a center seam on the back; however there are several side seam models in use. OPEN SIDE ENVELOPE: The open side envelope has its opening on the longer dimension and has either diagonal or twin side seams.