Wheelbarrows balance heavy loads to roll them between locations. They have either a sloped tray for bulk materials or a flat bed for crates, boxes, equipment, and other large items. Standard wheelbarrows rely on physical effort for rolling and dumping the load. Battery-powered wheelbarrows and carts have a motor that drives their wheels to assist with moving loads across long distances and up inclines. Wheelbarrow tires replace worn tires or change to a different size or material.