Door Knocker
Hand-Held Door Knocker for Mail Carriers, 1863, Smithsonian's National Postal Museum
Some letter carriers chose to use wooden, dumbbell-shaped door knockers on their rural delivery service rounds. Convenient, lightweight and easy to grasp, the knocker saved wear and tear on hands and sounded a loud crack to announce the carrier’s arrival.
The postman really did ring twice, or knocked, or blew a whistle. Letter carriers waited for someone to answer their signal, and if no one was home, they took the mail back to the post office and tried again the next day. Studies showed carriers spent an average of two hours daily waiting at the doorstep. To save work hours, the Post Office Department required residents to install mailboxes or letter slots in 1916.