Counterweights are the most satisfactory way of manually flying stage equipment and lighting, whether single- or double-purchase, and rear or front and rear guided. Single purchase counterweights should be employed where the travel available for the weight cradle is equivalent to that required for the barrel. In the double-purchase system the weight cradle travels only half the distance of that traveled by the barrel, which requires double the quantity of weights in the cradle, but it is ideal if additional wing space is required or when space on the stage wall is limited due to doorways or lack of height. The general principles are similar for all counterweights, with a system of suspension cables and hauling ropes passing over pulleys, a barrel flying at one end, and a guided weight cradle at the other end running inside a guarded wall frame.