A horse collar is a part of a horse harness that is used to distribute the load around a horse's neck and shoulders when pulling a wagon or plough. The collar often supports and pads a pair of curved metal or wood pieces, called hames, to which the traces of the harness are attached. The collar allows the horse to use its full strength when pulling, essentially enabling the horse to push forward with its hindquarters into the collar. If wearing a yoke or a breastcollar, it had to pull with its less-powerful shoulders. The collar had another advantage over the yoke as it reduced pressure on the horse's windpipe.