Allow me to make this really simple for you, because I'm trying to be delicate, but I always want to be funny, and that would be bad.
Woman has to use the restroom:
1. Enters restroom.
2. Uses first stall; must hold bottom of stall door to keep closed.
3. Must use toilet paper, which means she must release door, especially if she must do any other type of feminine hygiene maintenance
Problem: Door opens about 4-6 inches, allowing anyone entering the restroom to view anything she is doing.
Solution: A simple nail hook lock would suffice, or even a slide chain lock if there's not enough space for a nail hook. Sit down and give it a whirl, boys! ;)