over the transom

Etymology
A transom is a lintel or crosspiece over a door; likely an alteration of. Refers to the idea of a writer tossing a manuscript through the open window over the door of the publisher's office. Alternatively, a "transom" is the nautical term for the back of a small boat. Something which "came in over the transom" would have suddenly (and presumably, surprisingly) entered through the "back door" of the craft, metaphorically.

Prepositional phrase

 * 1)  Unsolicited.
 * All the over-the-transom articles are handled by our interns.
 * Only one piece that came in over the transom appears in this issue.
 * 1)  Meeting a deadline by delivery after the day of the deadline but before opening of business the following business day.
 * They worked into the night and sent an associate to make an over-the-transom filing.

Usage notes

 * This sees adjectival use ("a submission over the transom", "over-the-transom articles") and adverbial ("came in over the transom").