On the bit

The phrases "on the bit", "behind the bit" and "above the bit" are equestrian terms used to describe a horse's posture relative to the reins and the bridle bit. A position on the bit is submissive to the rider's rein aids, given through the bit. When a horse is behind the bit, the head is tucked too far down and rearward. If above the bit, then the head is too high.