Definition
A checkrein (or check rein) is a rein used to control the height of a horse's head. It is attached to the bit and runs to a point on the horse's back or harness, limiting how high the horse can raise its head. It's often used in driving horses for stylistic reasons. Unlike a bearing rein that subtly guides posture, a checkrein is more restrictive. It's akin to a gentle limiter.