K: Kneeling
When you first agreed to let your hotwife/hothusband lock your cock and to be their cuck, you had no idea how much time you would spend kneeling. You hoped to watch them from the comfortable chair in the bedroom -- you were even excited about that prospect. They soon figured out that it's more fun to have you naked and kneeling by the side of the bed, however, ready with lube whenever they need it, ready with your tongue for cleanup, kissing their feet or the bull's sweaty ass while they're going at it, or just to have you nearby so that your hothusband/hotwife can look you right in the eyes as they how much better their bull is than you. You never feel more intimate than in that moment!
It's not just that, though. Kneeling in their presence, even when they're not fucking or making love, is a sign of respect. They both believe that you should never meet the bull's eyes at his level -- instead, always look up at him. And, when they really want to put you in your place, they make you kneel outside the bedroom door when the bull makes your hothusband/hotwife moan and scream out his name.
Don't worry, though. If you're a good cuck, they might just buy you kneepads for your next birthday. After all, they do care about you -- just not as an equal.