Occupied!
There aren’t very many objectively bad things in this world. However, one of the few things everyone hates is public restrooms. For some reason, the locks never work, the door doesn’t swing shut all the way, and there’s always a tiny gap for people to look through.
If you ever find yourself in an emergency situation while out in public, you’re better off just holding it in. The last thing you want is to feel uncomfortable when you’re most vulnerable. Blocking the stall door with one foot won’t stop people from barging in and taking a gander at the goods.