Doorknob rattling is a practical foley effect built from real door hardware rather than a line from a film or show. Editors keep it in sound libraries because a few seconds of shaking tells a complete story about a locked door. It spread through short horror edits, escape room videos, gaming clips and meme sketches, often paired with door knocking, where the joke or scare depends on someone not getting in or out. Its realism is why it lasts, since viewers recognise the exact noise from their own homes.