Bar Code A series of vertical bars and half bars representing the zip code information for the delivery address on a piece of mail.

CASS - Coding Accuracy Support System A software program that verifies the accuracy of an address and supplies the +4 digits to an accurate zip code.

Direct Impression Addressing Addressing and applying a bar code directly onto a mail piece.

Endorsement Line Wording applied to the mail piece requesting new addresses and how the mail should be handled by the USPS. You must have a return address on the mail piece when using an endorsement line. The type must be 8 point or larger & must stand out clearly against the background. There is a fee and you should check with the Mail Information Center.

Flats (Flts) Flat size mail exceeds at least one of the following dimensions: 11-1/2" long, 6-1/8" high, 1/4" thick.

Indicia A printed designation on a mail piece that indicates postage payment.

Insert A letter, card, or other item placed in an envelope.

Letter Size Mail A mail piece that is no larger than 11-1/2" long, 6-1/8" high and its thickness does not exceed 1/4"

Machinable Envelope & Insert An envelope and insert(s) that are able to be put on an inserting machine rather than being handled by hand. Insert piece needs a minimum of 1/4" clearance of envelope, a 1/2" is totally in spec for machines. Remember: the more inserts the more clearance needed. Machinable materials saves on both time and money.

Machinable Mail Piece The suitability of a mail piece for sorting by mail processing equipment at the USPS.

Minimum Size of Any Mail 5" long, 3-1/2" high, .007 thick.

Non-Profit Mail Organizations that qualify for non-profit rates receive a postage rate that is less than standard mail. Non-profit mail is subject to inspection. Non-profit mail has very specific rules as to what can be mailed at non-profit rates - check first with your mailing house or the Mail Information Center.

Postcard Size Mail Maximum size of the mail piece is 6" long, 4-1/4 high, at least .007 thick.

Pre-Sort The process by which a mailer prepares mail by sorting it to the finest extent required for a specific postage rate.

Self-Mailer A mail piece that is self contained and does not require an envelope.

Standard Mail A mail piece that is not mailed as First-Class and weighs less than 16 oz. Formerly called Bulk Mail or Third Class mail.

Tab (Wafer Seal) A circular or rectangular item usually about 1/2 to 1" in size used to close a self-mailer.

USPS United States Postal Service.