Enclosure refers to thing or things put in an envelope with letter. It serves both as a check to the recipient of the letter that everything was actually enclosed and as a reminder to the letter writer of what was sent a The enclosure list Is type ed flush left spaces below the signature b. Some people prefer to use Encl. over Enclosure• Enclosure refers to thing or things put in an envelope with letter. It serves both as a check to the recipient of the letter that everything was actually enclosed and as a reminder to the letter writer of what was sent. a. The enclosure list is typed flush left, two spaces below the signature. b. Some people prefer to use Encl. over Enclosure