INDICIA - Postage permit located on the upper right corner of an envelope which is pre-printed and does not require a postage stamp.

INSIDE SIDE SEAM - Seam construction on Catalog or Booklet envelope where the seam glues beneath the back panel.

INSIDE TINT - Printed design on the inside of the envelope. Used for added opacity and/or for graphic interest.

INTER-OFFICE ENVELOPE - Usually an open end or catalog style envelope which is preprinted on both sides with lines depicting the person(s) and department that the envelope is to be delivered to. On a standard 10 x 13 size there are enough spaces to accommodate 56 deliveries. Eight 3/8" holes are drilled completely though the envelope for visible conformation of any contents. Button and string or Tac-N-Tac™ closures are used on this type of envelope.