1.) a machine-readable code typically in the form of parallel lines of variable height or spacing sprayed in a row on the front or back of a <#cover> by the <#usps=U.S. Postal Service> or mailer. The <#postnet=POSTNET> barcode is used to expedite the sorting and delivery of mail. Other barcodes are used for tracing and tracking mail and are used in <#indicia> for security purposes. 2.) a machine-readable code used by the <#bep=BEP> as part of their Electronic Stamp Inspection process. Barcodes are sprayed onto the margins of all <#coil> and <#booklet> <#stamp=stamps> to facilitate the identification and removal of defective stamps. While these bar codes are usually trimmed off in the manufacturing process, booklet panes do exist with a barcode on the <#tab>.