The calves are lined up in a row and moved through narrow runways leading to a chute with spring-loaded doors. When a calf enters the chute, a door is closed behind it and a lightweight rope, attached to a trip lever, is fastened around the calf's neck. The lever holds a taut cord or "barrier" that runs across a large pen or "box" at one side of the calf chute, where the horse and rider wait. The barrier is used to ensure that the calf gets a head start. When the roper is ready, he or she calls for the calf, and the chute operator pulls a lever opening the chute doors and releasing the calf. The calf runs out in a straight line. When the calf reaches the end of the rope, that trips the lever, the rope falls off the calf, and the barrier for the horse is released, starting the clock and allowing horse and rider to chase the calf.