Draw reins and running reins are pieces of riding equipment used for training that use the mechanical advantage of a 'single movable pulley' to cause the horse to bring its head down and inward. While a regular rein is the strap that attaches to the bit and is held by the rider, these types of reins slide through the bit ring, adding leverage to the rider's hands and arms, allowing the rider to force the horse's head into a desired position.