knock-knock (knocking sound)

knock (abrupt rapping sound) / (baseball) fungo

to knock / to press down on the rear end of a mechanical pencil and dispense lead

knockdown

to knock down

a revolving door

to hit; to strike; to beat; to paddle (to spank with a paddle) / to criticize; to verbally abuse or attack / to play (drums); to beat / to clap (hands) / (programming) to call (an API)

to use up money

Western-style door

platform door; platform screen door