Knocker (noun)

A device attached to a door, typically made of metal or wood, that is used for knocking or announcing one's presence.

Origin:

From the verb knock, which means to hit a surface with force, and the suffix -er, used to indicate a person or thing that performs an action.

Examples:

1. He knocked on the door with the brass knocker.
2. The knocker on the old wooden door was worn and tarnished.
3. The knocker on the front door was in the shape of a lion's head.
4. The knocker was so heavy that it made a loud sound when used.
5. He replaced the old knocker with a new one, which had a more modern design.