A carabiner or karabiner is a metal loop with a sprung or screwed gate. The loop part opposite the gate is referred to as the spine. It can quickly and reversibly connect components in safety-critical systems. The word comes from "Karabinerhaken", meaning "hook for a carbine" in German.
The term "carabiner" was not adopted as an English word for some time. According to Fergus Fleming's book on the beginning of alpinism, Killing Dragons: The conquest of the Alps, the early British climbers derided aids like carabiners, ice axes and crampons leaving their development to Italian, French and other alpinists.
Carabiners are widely used in sports requiring ropework, such as climbing, slacklining, caving ("Single Rope Technique"), canyoning, sailing, and canoeing; and in industrial rope access work, such as construction or window cleaning.
Carabiners used in sports tend to be lighter than carabiners used in industry. For recreational climbing, almost all carabiners are made from 7075 aluminum and are treated to a T6 temper (solution treated and then artificially aged). For rope rescues and industrial uses, where the weight of the carabiner is not an important factor and larger working loads are encountered, steel carabiners are commonly used. Some carabiners used in industry do not have a sprung swinging gate but have a screw shut gate that generally can be opened and closed only using a special tool.
Carabiners have also found a place in popular usage as key holders, and as water-bottle holders for hikers.
When sold for use in climbing in Europe, carabiners must conform to standard EN 12275:1998 "Mountaineering equipment - Connectors - Safety requirements and test methods," which governs testing protocols, rated strengths, and markings. A breaking stress of at least 20 kN (20,000 newtons = approximately 4,500 pounds of force which is significantly more than the weight of a small car) with the gate closed and 7 kN with the gate open is the standard for most climbing applications, although requirements vary depending on the activity. Carabiners are marked on the side with single letters showing their intended area of use, for example, K (via ferrata), B (base), and H (for belaying with an Italian or Munter hitch).
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