I often have guests or subletters in my apartment, so I needed a way to store my stuff without having to remove it altogether. I'm lucky enough to have a very large closet in my bedroom, so I decided to put a lock on it.
The only problem is that the door is a single sliding closet door. With the help of my favorite hardware store guys, I devised a solution: I took a mailbox lock, which has an arm that flips down, and filed a notch in the arm. Then I installed a strike plate on the jamb with a recess behind it. When you turn the key on the lock, the arm flips down and the notch catches on the strike plate, locking the door from sliding open.