One of my own college-aged kids is having a problem with his roommates stealing the food that he buys. Seems like nothing has changed from the seventies.

Anyway, he's in a dorm situation where there are 4 bedrooms and a common kitchen to an apartment and none of the boys have a seven-day meal plan on campus. When he has confronted his roommates, they get angry and say they don't have any money so why shouldn't they eat his, etc.
I seem to recall a thread years ago in which people talked about this problem and creative ways they solved it. I can't find the thread; does anyone have any ideas?