Figure-eight devices are climbing and rescue tools designed to create a controlled descent or to belay a climber. They are shaped like the number eight and are typically made of metal, allowing for smooth rope movement. These devices are commonly used in activities such as rock climbing, canyoneering, and caving. When using a figure-eight device, the rope is threaded through the device, which helps manage friction and control the speed of descent. Proper use of a figure-eight device is essential for safety, making it a fundamental piece of equipment for climbers and rescue professionals alike, including mountain rescue teams.