Hidden your knob in the door
If you don’t wanna anyone to disturb you, you might hang a signal on the doorknob to tell them. But there’s always some careless man. So you still might be disturbed by them. What you need is a doorknob like this. While you wanna take a rest, just pull it from the inside and it’s totally unavailable. You’re safe.
Designer: Arnaud Lapierre