This is just a binding design. A kneeler would be mounted on the floor, a pair. The palm of the hand rests on the flat part, and the cylinder moves down and locks.
They work as "hand rests" for a person on hands and knees ... but when the bar is in place the hand can't be removed. There's a faint outline of a hand in this image (if that helps it make more sense). I'll have to upload a better picture some other day.