Envelope seam construction affects an envelope’s strength, appearance, and machine compatibility. The main types are: side seam (seams run vertically on both side edges — strongest, ideal for checks and heavy contents), diagonal/center seam (seams meet at an angle in the back center — standard for most business envelopes), and the open-end vs. open-side distinction (whether the opening is on the short or long edge — critical for inserting equipment). The interactive guide below illustrates each seam type visually.
Envelope Seam Types Compared
- Side seam: Seams along both vertical edges. Strongest construction — best for checks, coins, and heavy items.
- Diagonal (center) seam: Traditional seam that meets at an angle in the back center. Standard for most business and personal envelopes.
- Baronial seam: Deep V-flap seam style common in greeting card and invitation envelopes.
- Open end vs. open side: Open-end opens on the short edge; open-side opens on the long edge — important for machine inserter compatibility.
Need help choosing the right construction? Shop our envelopes or use the envelope finder.
