After the race completes, racehorses are freed from the sleds and led to the back yard, while the sleds are returned to the starting gate with the aid of a trolley. The amount of weight a horse must pull is determined by several factors, with younger horses and mares pulling less than older horses and stallions. A horse's group and rating—which further determines the required weight—depends upon the amount of money the horse has previously earned. Horses compete in groups labeled 1–26, and groups are rated with Open, A1, A2, B1, B2, B3, B4, C1, C2 or D (in order of decreasing winnings). This is like system used in Japanese thoroughbred racing. The weight allowance of jockeys is either , based on the number of wins.