Using models built for a Museum in Rigby, Idaho, this page illustrates three variations on the basic hay derrick

These derricks all operated on the same principle. Pulleys were attached with chains to the boom pole and to the derrick frame. A Jackson Fork for lifting the hay was attached to a cable threaded through the pulleys. This cable was pulled in the early days by a horse or a team of horses. The Jackson Fork was set in the hay and latched. The horse or horses pulled until the hay was free in the air. The boom was swung around until the hay was over the haystack. And the man on the hay wagon jerked the trip rope that dumped the hay onto the stack.