Knocking sounds have long been used in audio editing, radio, film and online video to signal arrival, interruption or off-screen action. On soundboards and meme pages, a plain knocking clip stays popular because it is easy to understand in almost any context. Creators use it in prank calls, fake doorstep skits, gaming edits and short reaction videos. Its staying power comes from how universal the cue is: a few quick knocks immediately tell the audience that someone is outside or trying to get attention.