This is an old MobilityWod episode that has a great drill. It’s the second one where he props his leg on the arm of the couch. I don’t think this is ever brought up again in any of his follow up videos, but I think it’s such a great drill!
When you’re doing this, think of your hip joint as a simple ball bearing joint:
Imagine that around that “ball” and along the inside of the socket, there’s a bunch of “junk”. You are trying to clear out all of that junk so that the ball can rotate freely and properly within the joint. Additionally, you also have to realize the muscles are attached all over the place on the femur and that these biological pieces (muscles, tendons, ligaments) that are attached are sometimes short/tight and they will prevent the ball from moving “freely”.
Your goal is not only to clear the actual socket and ball bearing, but also to stretch the tissues that are restricting certain degrees of movement.
Propping your leg on the couch or on a bed gives you the control to run the femur through all kinds of ROM in order to clear the jump and stretch any and all tissues depending on what angle you’re applying force. That’s why Kelly always talks about “hunting”. You have to move that femur in a way that encompasses full ROM. Both in a manner that’s “linear” like in a squat, and in a manner that’s “rotary” like in a roundhouse kick.