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.