Angelina what would you think of the idea of a sealed envelope? but even for that he needs a key holder to sign the seal in a forgery-proof way
Without a keyholder to sign it, it seems too easy/low-cost to replace, to the point where you might as well just carry the key with you by itself. Which is an option, if you just need the cage as a reminder to play nice, or if the hassle of retrieving the key is enough to knock you out of the mood.
With a keyholder, it is an option, but that requires another person to willingly take part in your cage use and actually wanting to discourage you from masturbating. Of course no boy wants to admit to a family member (other than maybe a brother of similar age) how he has been wanking, but that would be ineffective if said family member never asks to see the envelope.
Plus heaving that sealed envelope also serves as at least a little guarantee that the dynamic will not be getting out of hand, as you can break it off if unreasonable demands are made.
