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Abseiling ( /ˈæbseɪl/ AB-sayl or /ˈɑːpzaɪl/ AHP-zyle; from German abseilen 'to rope down'), also known as rappelling ( /ræˈpɛl/ RAP-pel or /rəˈpɛl/ rə-PELL; from French rappeler 'to recall, to pull through'), is the controlled descent of a steep slope, such as a rock face, by moving down a rope. When abseiling the person descending controls their own movement down the rope, in contrast to lowering off in which the rope attached to the person descending is paid out by their belayer.
The technique is used by climbers, mountaineers, cavers, canyoners, search and rescue and rope access technicians to descend cliffs or slopes when they are too steep and/or dangerous to descend without protection. Many climbers use this technique to protect established anchors from damage. Rope access technicians also use this as a method to access difficult-to-reach areas from above for various industrial applications like maintenance, construction, inspection and welding. 
To descend safely, abseilers use a variety of techniques to increase the friction on the rope to the point where it can be controlled comfortably. These techniques range from wrapping the rope around their body (e.g. the Dülfersitz technique) to using custom-built devices like a rack or a figure of 8. Practitioners choose a technique based on speed, safety, weight and other circumstantial concerns.
In the United States, the term "rappelling" is used.   In the United Kingdom, both terms are understood,  but "abseiling" is more common.   In Australia, New Zealand and Canada, the two terms are used interchangeably. Globally, the term "rappelling" appears in books written in English more often than "abseiling". 
The origin of the term rappel in reference to the technique is attributed by Roger Frison-Roche  Frison in turn attributed the technique of abseiling to Jean Charlet-Straton , a Chamonix guide who lived from 1840 to 1925. Charlet originally devised the technique during a failed solo attempt of Petit Dru in 1876.  After many attempts, some of them solo, he managed to reach the summit of the Petit Dru in 1879 in the company of two other hired Chamonix guides, Prosper Payot and Frédéric Folliguet. During that ascent, Charlet mastered the technique.[ citation needed ]circa 1944.
Abseiling is used in a number of applications, including:
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 abseiling, most commonly due to failing anchors.  An analysis of American Alpine Club accident reports shows that this is followed by inadequate safety backups and rappelling off the ends of ropes. 
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.  
Traditional climbing is a style of rock climbing in which the climber places all the necessary protection gear required to arrest any falls as they are climbing, and then removes it when the pitch is complete. Traditional bolted aid climbing means the bolts were placed while on lead and/or with hand drills. Traditional climbing carries a higher level of risk than bolted sport climbing, as the climber may not have placed the safety equipment correctly while trying to ascend the route, or – in some cases – there may be no protection available to keep a climber from a ground fall or serious injury. For some of the world's hardest climbs, there may not be sufficient cracks or features in the rock that can accept protection gear, and the climb can only be safely attempted by bolting as a sport climb.
This is an index of topics related to climbing.
This glossary of climbing terms is a list of definitions of terms and jargon related to rock climbing and mountaineering. The specific terms used can vary considerably between different English-speaking countries; many of the phrases described here are particular to the United States and the United Kingdom.
Ice climbing is the activity of ascending inclined ice formations. Usually, ice climbing refers to roped and protected climbing of features such as icefalls, frozen waterfalls, and cliffs and rock slabs covered with ice refrozen from flows of water.
Rock-climbing equipment requires a range of specialized sports equipment, for training, for aid climbing, and for free climbing. Developments in rock-climbing equipment played an important role in the history of rock climbing, enabling climbers to ascend more difficult climbing routes safely, and materially improving the strength, conditioning, and ability of climbers.
Belaying is a variety of techniques climbers use to create friction within a climbing system, particularly on a climbing rope, so that a falling climber does not fall very far. A climbing partner typically applies tension at the other end of the rope whenever the climber is not moving, and removes the tension from the rope whenever the climber needs more rope to continue climbing.
Rock climbing is a sport in which participants climb up, across, or down natural rock formations. The goal is to reach the summit of a formation or the endpoint of a usually pre-defined route without falling. Rock climbing is a physically and mentally demanding sport, one that often tests a climber's strength, endurance, agility and balance along with mental control. Knowledge of proper climbing techniques and the use of specialized climbing equipment is crucial for the safe completion of routes.
The Munter hitch, also known as the Italian hitch, mezzo barcaiolo or the crossing hitch, is a simple adjustable knot, commonly used by climbers, cavers, and rescuers to control friction in a life-lining or belay system. To climbers, this hitch is also known as HMS, the abbreviation for the German term Halbmastwurfsicherung, meaning half clove hitch belay. This technique can be used with a special "pear-shaped" HMS locking carabiner, or any locking carabiner wide enough to take two turns of the rope.
A Prusik is a friction hitch or knot used to attach a loop of cord around a rope, applied in climbing, canyoneering, mountaineering, caving, rope rescue, ziplining, and by arborists. The term Prusik is a name for both the loops of cord used to tie the hitch and the hitch itself, and the verb is "to prusik". More casually, the term is used for any friction hitch or device that can grab a rope. Due to the pronunciation, the word is often misspelled Prussik, Prussick, or Prussic.
Australian abseiling is the process of descending a fixed rope (abseiling) in a standing position while facing the ground.
Single-rope technique (SRT) is a set of methods used to descend and ascend on the same single rope. Single-rope technique is used in caving, potholing, rock climbing, canyoning, roped access for building maintenance and by arborists for tree climbing, although to avoid confusion in the tree climbing community, many have taken to calling it "stationary" rope technique.
An autoblock is a rope device used in climbing and caving for both rappelling (downward) and ascending (upward).
A Reverso is a belay device developed and patented by Petzl, used for example in rock-climbing and other activities which involves rope-work. Another version of this device is the Reversino, intended for use with thinner ropes.
A dynamic rope is a specially constructed, somewhat elastic rope used primarily in rock climbing, ice climbing, and mountaineering. This elasticity, or stretch, is the property that makes the rope dynamic—in contrast to a static rope that has only slight elongation under load. Greater elasticity allows a dynamic rope to more slowly absorb the energy of a sudden load, such from arresting a climber's fall, by reducing the peak force on the rope and thus the probability of the rope's catastrophic failure. A kernmantle rope is the most common type of dynamic rope now used. Since 1945, nylon has, because of its superior durability and strength, replaced all natural materials in climbing rope.
A belay device is a mechanical piece of climbing equipment used to control a rope during belaying. It is designed to improve belay safety for the climber by allowing the belayer to manage their duties with minimal physical effort. With the right belay device, a small, weak climber can easily arrest the fall of a much heavier partner. Belay devices act as a friction brake, so that when a climber falls with any slack in the rope, the fall is brought to a stop.
The South African Abseil or South African Double Roped Classical Abseil is a modern variation of the non-mechanical classical abseil method used by mountaineers and rock climbers to quickly descend steep terrain by sliding down a rope wrapped around their body to create controlled friction.
The figure 8 belay device is a piece of metal in the shape of an 8 with one large end and one small end.
In July 1936, five climbers died while attempting to ascend the north face of the Eiger mountain in Switzerland.
The Dülfersitz, also known as body rappel is a classical, or non-mechanical abseiling technique, used in rock climbing and mountaineering. It is not used frequently any more, since the introduction of belay devices. In the Dülfersitz, the rope is wound around the body, and the speed of descent is controlled using the friction of the rope against the body.
Alpine climbing is a branch of climbing in which the primary aim is very often to reach the summit of a mountain. In order to do this high rock faces or pinnacles requiring several lengths of climbing rope must be ascended. Often mobile, intermediate climbing protection has to be used in addition to the pitons usually in place on the climbing routes.