Related
 No Wank
 Cum Control
 Cages

Great for keeping horny, with little he can do about it.
Good for exhibitionism, with little restrictions to toilet functions.
In addition a leather sheath could be laced up on the puppy for the extra layer of security.

I like these kinds of devices, unlike the Cock Cuff, they allow the full expression of the boys hard-on. Its trapped there, pumping and with his pre-cum dribbling. Not massively suitable for him to piss through, although possible.

This would suit a slave that liked cages and iron work.