abseiling...

Abseiling (German: abseilen, "to rope down"), rappelling in American English,[1] is the controlled descent down a rope; climbers use this technique when a cliff or slope is too steep and/or dangerous to descend without protection. Abseiling is used chiefly in British English, while other Anglophone countries, except Australia and New Zealand, use different terms.

History
The origin of the abseil is attributed to Jean Estéril Charlet, a Chamonix guide who lived from 1840-1925. Charlet originally devised the technique of the abseil (or rappel) method of roping down during a failed solo attempt of Petit Dru in 1876. After many attempts, some of them solo, he managed to summit the Petit Dru in 1879 in the company of two other Chamonix guides, Prosper Payot and Frédéric Folliguet, whom he hired (a rather paradoxical move for a guide). During that ascent, Charlet perfected the abseil.

Equipment
Ropes: Climbers often simply use their climbing ropes for rappelling. For many other applications, low-stretch rope (typically ~2% stretch when under the load of a typical bodyweight) called static rope is used to reduce bouncing and to allow easier ascending of the rope.

Anchors for rappelling are sometimes made with trees or boulders, using webbing and cordellete, or also with rock climbing equipment, such as nuts, hexes and spring loaded camming devices. Some climbing areas have fixed anchors for rappelling.

A descender or rappel device is a friction device or friction hitch that allows rope to be paid out in a controlled fashion, under load, with a minimal effort by the person controlling it. The speed at which the rappeller descends is controlled by applying greater or lesser force on the rope below the device or altering the angle at which the rope exits the device. Descenders can be task-designed or improvised from other equipment. Mechanical descenders include braking bars, the figure eight, the abseil rack, the "bobbin" (and its self-locking variant the "stop"), the gold tail, and the "sky genie" used by some window-washers and wildfire firefighters. Some improvised descenders include the Munter hitch, a carabiner wrap, the basic crossed-carabiner brake and the piton bar brake (sometimes called the carabiner and piton). There is an older, more uncomfortable, method of wrapping the rope around one's body for friction instead of using a descender, as in the Dulfersitz or Geneva methods used by climbers in the 1960s.

A climbing harness is often used around the waist to secure the descender. A comfortable climbing harness is important for descents that may take many hours.

A prusik might be used as safety back-up.

Helmets are worn to protect the head from bumps and falling rocks. A light source may be mounted on the helmet in order to keep the hands free in unlit areas.

Gloves protect hands from the rope and from hits with the wall. They are mainly used by recreational abseilers, industrial access practitioners, adventure racers and military as opposed to climbers or mountaineers. In fact, they can increase the risk of accident by becoming caught in the descender in certain situations.

Boots or other sturdy footwear with good grips.

Knee-pads (and sometimes elbow-pads) are popular in some applications for the protection of joints during crawls or hits.

Application
Abseiling is used in a number of applications, including:
• Climbing, for returning to the base of a climb or to a point where one can try a new route.
• Recreational abseiling.
• Canyoning, where jumping waterfalls or cliffs may be too dangerous.
• Caving and Speleology, where underground pitches are accessed using this method (Single Rope Technique).
• Adventure racing, where events often include abseiling and other rope work.
• Industrial/Commercial applications, where abseiling techniques are used to access parts of structures or buildings so as to perform maintenance, cleaning or construction, e.g. steeplejacking, window cleaning, etc.)
• Access to wildfires.
• Confined spaces access, such as investigating ballast tanks and other areas of ships.
• Rescue applications, such as accessing injured people or accident sites (vehicle or aircraft) and extracting the casualty using abseiling techniques.
• (Military) Tactical heliborne insertion of troops and special forces into the battlefield close to the objective when proper landing zones are not available. More commonly used in urban warfare scenarios and is increasingly replaced by fast-roping. Typical examples include: insertion into urban environments, boarding (attack) of sea-going vessels and insertion of forces to seize and secure a landing zone in enemy territory (airhead assault).

Safety and Ecological Issues
Abseiling can be dangerous, and presents risks, especially to unsupervised or inexperienced abseilers. According to German mountaineer Pit Schubert, about 25% of climbing deaths occur during rappelling, most commonly due to failing anchors. Another frequent cause of accidents is abseiling beyond the end of the rope.
Abseiling is prohibited or discouraged in some areas, due to the potential for environmental damage and/or conflict with climbers heading upwards, or the danger to people on the ground.