Parts of an Envelope

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How an Envelope is Constructed

Envelope Parts
Most envelopes have all these parts.

Face or Front
The front of the envelope, usually seamless, where the address, postage, cancellation stamp, and usually the return address appear.

The back of the envelope where the flaps meet to form and seal the envelope.

  1. Seal Adhesive: Where the gum or glue goes for sealing the envelope after inserting contents.
  2. Top Flap: Also known as the seal flap, it is folded down and sealed after inserting contents.
  3. Top Fold: Usually scored during manufacturing, this crease is where the top flap is folded to seal the envelope.
  4. Throat: The space between the top fold and top of the back flap that forms the opening where envelope contents are inserted.
  5. Side Flaps: The sides of the envelope folded to the inside and sealed along the back flap to form a pocket.
  6. Side Folds: The creases along the sides of the envelope separating the envelope face from the side flaps folded to the back.
  7. Shoulders: A portion of the side flaps along the throat where they meet the top fold.
  8. Bottom Flap: That portion of the envelope folded up and sealed along the edges of the side flaps to form a pocket.
  9. Seam Overlap: Where two or more flaps overlap.
  10. Bottom Fold: The crease along the bottom of the envelope separating the envelope face from the bottom flap.

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Envelope Flaps

Envelope Flaps
Flap styles affect appearance and functionality of the envelope.

The parts of an envelope that are folded, overlapped, and sealed to enclose the contents are called flaps. Flaps are usually rectangular or triangular with rounded, tapered, or pointed corners. The typical envelope consists of two side flaps, a bottom flap, and a top flap. The side flaps are folded in first with the bottom flap folded up. They are sealed where they overlap. The top flap is folded over the side and bottom flaps and sealed after inserting the envelope contents.

Envelope styles are typically defined by their style of top flaps:

  • Commercial flaps are rectangular with tapered sides, rounded corners, and a shallow, rounded point.
  • Wallet flaps are rectangular with slightly tapered sides and rounded corners.
  • Square flaps are square or rectangular with fairly straight sides and non-rounded corners.
  • Pointed flaps are triangular with a pointed or slightly rounded off corner.

There are variations to these basic flap styles, such as extra large square or wallet flaps and some types of business reply or remittance envelopes that include a tear-off section on the flap. The choice of envelope flaps not only affects appearance, but is an important consideration when using automated equipment which may require certain sizes and styles of flaps. Some automatic-insertion machines may only support standard flap sizes and shapes.

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Envelope Seams

Envelope Seams
Seams can affect the placement of printing on an envelope.

The seams are the edges where the envelope flaps meet and overlap. The style of flaps determines the type of seams. The choice of seams can be a determining factor in the placement of printing on an envelope.

  • Diagonal Seams
    Envelopes with pointed or triangular flaps create diagonal seams across the back of the envelope.
  • Side Seams
    Running close to the outer edge of the envelope, square or rectangular flaps form side seams. Side seams provide a larger printing area.
  • Center Seam
    Found on catalog style envelopes, large square or rectangluar side flaps meet and overlap in the center of the envelope. Smaller square or wallet top and bottom flaps folds over top and bottom edges of the side flaps.
  • Seam Overlap
    That portion of the bottom flap that overlaps the side flaps (or where two side flaps meet for a center seam) forms the seams of the envelope.

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Envelope Openings

Envelope Openings
The opening is determined by the length of the side where the opening appears.

Envelopes have one side left open and unsealed for inserting material. Non-square envelopes are either open end or open side. Open side is the most common, even though most letter mail envelopes appear to open on top. The opening is determined not by orientation of the top flap but by the length of the side where the opening appears.

  • Open Side
    On rectangular envelopes, when the top flap (opening) is on the long side of the envelope, it is considered an open side.
  • Open End
    Open end envelopes have the top flap and opening on the short side of the envelope. Catalog envelopes are typically open end as are many specialty envelopes such as coin envelopes, policy envelopes, and some interoffice envelopes.

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Envelope Styles

Envelope Styles
Most envelopes fall into one of these six styles.

Although envelopes can be custom-ordered in any almost any size, there are numerous standard styles, each with its own standard sizes.

The size and shape of the flaps and type of seams combine to form six main types of envelopes used for the bulk of non-specialty applications.

  • A-Style or Announcement Envelopes
    Open side envelopes with square, often deep flaps and side seams. Sometimes with deep pointed flaps and diagonal seams.
  • Baronial Envelopes
    Open side, almost square envelopes with pointed flaps and diagonal seams.
  • Booklet Envelopes
    Open side envelopes with small square flaps and side seams.
  • Catalog Envelopes
    Usually open end envelopes with wallet style flaps and center seams.
  • Commercial Envelopes
    Open side envelopes with commercial style flaps and diagonal seams. The typical #10 envelope for business and personal mail is a commercial style envelope. The Monarch is a variation of the #7 3/4 envelope but with pointed flap.
  • Square Envelopes
    Large square flaps and side seams.
    • The links for each style go to a gallery showing the relative size of different envelopes along with dimensions for common envelopes sizes and their enclosures.

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Your Citation
Bear, Jacci Howard. "Parts of an Envelope." ThoughtCo, Jun. 30, 2014, Bear, Jacci Howard. (2014, June 30). Parts of an Envelope. Retrieved from Bear, Jacci Howard. "Parts of an Envelope." ThoughtCo. (accessed September 24, 2017).