It’s something he mostly does, as it is a bit challenging! You simply push one through then the other. If his sack is tight it sometimes takes a minute to loosen up. Once both balls are through his cock can be pushed through afterwards. It’s how it works for any solid cock and ball ring basically. But the big advantage is no pinching hairs or skin like on the hinged or plastic alternatives.
The thing is, for edging we just leave the ring on! So if I take the cage off the ring almost always stays and acts like a super solid cock and ball ring, which is brilliant.