My random roommate is renting his spot in the apartment to some other random guy for the month. I suspect that this random guy is using my soap, which is fucking nasty. I don't care if he uses my mustard, but soap is personal.
It would be easy for me to confront him about it. "Hey buddy, don't use my soap." If he said he wasn't, I'd say, "Ok." But merely asking him would be too simple and nice. For certain things, a lesson must be taught. He should know that you don't share a bar of soap with a random stranger. If he doesn't I will teach him.
While finishing up my shower, I plucked out a plethora of pubes and placed them on the soap. This serves two purposes. If the pubes remain, he's obviously not using my soap. If not, he's learned a valuable lesson: if you want to share my soap, you gotta peel off my pubes. And if I find additional pubes, I'm gonna jam that soap so far up his ass, he'll be sweating out soap for a long time and won't have to use mine.