A zip-line consists of a pulley suspended on a cable, usually made of stainless steel, mounted on a slope. It is designed to enable a user propelled by gravity to travel from the top to the bottom of the inclined cable by holding on to, or attaching to, the freely moving pulley. Zip-lines come in many forms, most often used as a means of entertainment. They may be short and low, intended for child’s play and found on some playgrounds. Longer and higher rides are often used as a means of accessing remote areas, such as a rainforest canopy. Zip line tours are becoming popular vacation activities, found at outdoor adventure camps or upscale resorts, where they may be an element on a larger challenge or ropes course.