My girlfriend's favorite thing to do is to lock my (her) cock up in a chastity device. She uses the Curve device on me. Usually she keeps a small metal padlock on it, although if I have to travel by air, she will substitute a plastic, numbered lock. Keeping me caged and helpless, tagged like an animal, is a huge turn-on for her. The longest she has kept me locked up without release (so far) is about 10 days. Of course, she masturbates regularly, and taunts me about it.