A zip-line (also known as a flying fox, zip wire, aerial runway, eath slide or tyrolean crossing) consists of a pulley suspended on a cable mounted on an incline. They are designed to enable a user propelled by gravity to traverse from the top to the bottom of the inclined cable, usually made of stainless steel, by holding on 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 unusual areas (a rainforest canopy for instance) or found at outdoor adventure camps where they are usually one element on a larger challenge or ropes course.