>>10790968>>10790997Western European and probably American houses often have these things behind the doors to stop them from banging into the wall when swung open. If it wasn't there the door handle could dent the wall. It's a spring with a rubber cap and a lot of people in their childhood would sit there and flick the spring so it danced around creating the "Erdudueururudududdidmemurdururududrurudududruruuddududmddudmdudur" sound.
It was the thing you would sit on the floor and play with while tears rolled down your face and you got an ass whooping from your parents.