(in the bathroom.)
We need red lights on the outside of public restrooms so that you can flip the switch and warn others that serious business is taking place.
Do Not Enter.
You go in and someone else is already in there "en train de chier", to put it politely.
They hear you come in and then sit there silently waiting.
As a result I waste my time dropping drawers. What in hell can I do while you're sitting there waiting for me??