Diagonal Seams - Commonly used in correspondence commercials and pointed flap announcements.  This seam style is a workhorse and generally well-suited for applications involving mechanical insertion equipment, laser printing and postal meters.

Side Seams - These seams allow for a large, uninterrupted printing area on both front and back of the envelope.  Mostly found on booklets, square flap and commercial envelopes.  Commercial sizes are suitable for some laser and inserting applications.

Center Seams - this seam is located in the center of the envelope, adding strength for carrying heaver inserts to its design.  Envelopes with a center seam generally are not suitable for automatic insertion equipment or postage meter applications.

Single Side Seams - Seam is placed parallel to the edge of the envelope.  Usually found in open end style envelopes (with or without a flap).  Allows a larger printing area unobstructed by seams or multiple paper thickness.  Recommended for manual insertion.