Abstract: A letter sheet includes a body portion which is foldable about itself so as to form at least two intermediate panels positioned between a pair of outer panels. Removable flange portions extend along and are detachably secured to the edges of the body portion which constitute the outer panels. The body portion is provided with a line of perforation along substantially the entire length of the edges of the outer panels. At least one of the removable portions on one of the outer panels is adapted to overlie the corresponding removable flange portion of the other of the outer panels when the sheet is in its folded condition. Connector means are associated with the removable flange portions for joining the overlying flange portions to thereby seal the folded letter sheet for postage.