Piton
In climbing, a piton (; also called a pin or peg) is a metal spike (usually steel) that is driven into a crack or seam in the climbing surface with a climbing hammer, and which acts as an anchor to either protect the climber against the consequences of a fall or to assist progress in aid climbing. Pitons are equipped with an eye hole or a ring to which a carabiner is attached; the carabiner can then be directly or indirectly attached to a climbing rope. Pitons were the original form of protection and are still used where there is  no alternative. Repeated hammering and extraction of pitons damages the rock, and climbers who subscribe to the clean climbing ethic avoid their use as much as possible. With the popularization of clean climbing in the 1970s, pitons were largely replaced by faster and easier-to-use clean protection, such as nuts and camming devices. Pitons are still found in place (as "fixed" pitons) on some established free climbing routes, as fixed belay station anchors, in places where nuts or cams do not work; and are used on some hard aid climbs. Styles and shapes. Pitons are sized and manufactured to  fit a wide range of cracks. From small to large, the most common are: Materials and evolution. Early pitons were made of malleable iron and soft steel and would deform to the shape of the crack when driven into the rock, which worked well in the irregular cracks found on European limestone. Soft pitons are difficult to remove without damaging the piton, so they were frequently left in place and became fixed anchor points on a climb. During climbing exploration of the hard granite in Yosemite Valley in the 1950s and 1960s, it was found that soft pitons did not  work very well. The long routes developed in Yosemite made it impractical and costly to fix routes, and the soft pitons were not durable enough to be placed and removed more than a few times. Pitons needed to be removed and used again on subsequent pitches, sometimes many times. Leaving gear in place went against the ethics of many climbers. John Salathé pioneered designs using hardened steel which were much tougher than the European pitons. Salathé's pins, which he developed for a climb of the Lost Arrow, resisted deformation and were easier to remove and reuse, and were durable  enough to be reused indefinitely.