Low-tech solution to doors that don't stay closed

I live in a house with five other people. Folks are always coming and going, and they aren't always conscientious about closing the doors behind them, whether to keep air conditioning inside, to keep pets out of some rooms, or just for privacy. Beyond that, some doors just don't stay shut.


We found a simple way to keep our door closed that makes everyone happy (except the dogs). It just took two wood screws and a long spring salvaged from a screen door that was being thrown out around the corner. Cut the spring to the right size, mount one side to the outside corner of the door, and the other attaches to the door frame.

Screen doors are known for slamming shut, but ours closes gently and stays shut.