Door knocks are one of the most widely used everyday sound effects in online video, because the sound is instantly understood without any explanation. Creators reuse the same short knock in comedy sketches, prank edits, reaction videos, horror shorts and gaming streams whenever a scene needs an arrival, an interruption or a moment of suspense. Its simplicity is the reason it has stayed popular: it fits almost any setting, from a house or office to a classroom, and it works just as well as a punchline setup as it does as a scare cue.