Are you tired of dealing with the "Do Not Disturb" signs when staying at a hotel? Then the "Doorknob Condition" will definitely come in handy. Here's how it works:
Well designer Arnaud Lapierre decided that wasn't enough, so he put together the Doorknob Condition, which is a doorknob that uses a pulley system to retract the entire doorknob, preventing anybody from getting in without breaking down the door[via Geekologie]
