This is what is known in the business as a male chastity belt.
What it does, right, is stop a male penis from entering withinside a foreign body.
What it doesn’t do, however, is stop a foreign body – a penis, for example – from entering withinside the back bottom of the wearer. Coz there’s a big hole in it, meant for number 2s, but which can be exploited for bumming. Though what you won’t get is freedom of much movement etc. blah.
Of interest is the fact that one can still have a wet wee whilst wearing it, and it comes in different sizes in order to accommodate one’s front bottom, including tumescence. Naturally.
This is what it looks like on a person who has both a front and a back bottom:
And if you would like to own one of these, go here. Not cheap, mind.