A piton (; also called pin or peg) in climbing is a metal spike (usually steel) that is driven into a crack or seam in the climbing surface using a climbing hammer, and which acts as an anchor for protecting the climber against the consequences of falling 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 connected 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 damage 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: RURP (Realized Ultimate Reality Piton) – a tiny piton the size of a postage stamp used in thin, shallow seams. It was designed by Tom Frost and Yvon Chouinard in 1959, and was manufactured by Chouinard Equipment in the 1960s. It is not a strong piece, and is mainly used for aid climbing, although it can feature as protection on extreme free routes (e.g. Rurp The Wild Berserk (E6 6b) at The Brand, Leicestershire, UK). More recent versions of the RURP include Bird Beaks and Peckers. Knifeblade – also known as Bugaboos, are thin straight pitons, that work in thin, deep cracks. Lost Arrow – designed by John Salathé and Yvon Chouinard, is a hot-forged, tapered piton that performs well in medium-size cracks. Angle – A piton made of steel sheet bent into a "U", "V", or "Z" shape; work well for larger cracks, where the steel deforms elastically as the piton is placed. Bongs – The largest pitons are angles made from aluminium sheet called bongs, named for the sound they produce while being hammered into place, or the sound they make when dropped. Bongs have become rare with the