Teaching a yearling to yield its hindquarters — to move its hind end away from pressure, crossing the hind legs as it does — is one of the most practically important groundwork exercises because it gives the handler the ability to control the horse's most powerful and potentially dangerous end from the ground. A horse that yields its hindquarters reliably and softly in response to light pressure on the halter or light touch on the flank is a horse that can be safely repositioned, can be stopped from kicking out, and has begun to understand the concept of moving away from pressure that will underlie all future training.
The exercise begins by standing at the yearling's shoulder, facing its hindquarters, with the lead rope in the hand closest to the horse's head. Apply gentle pressure on the lead rope to flex the nose toward you slightly, which disengages the horse from going forward, then use the other hand or a light touch of the fingertips on the horse's flank — just behind where a rider's leg would hang — to suggest movement of the hindquarters away from you. The moment the inside hind leg crosses over the outside hind leg, release all pressure completely and allow the horse to stand.
The release must be immediate and complete — even one step of correct crossing should earn a full release and a moment of rest. Over many repetitions, the horse learns that moving the hindquarters away from the pressure produces the release, and the exercise becomes softer and more responsive. The goal is eventually a horse that will yield the hindquarters from a light shift of the handler's body weight and eyes rather than requiring physical pressure on the flank.