In climbing, a bolt is a permanent anchor fixed into a hole drilled in the rock, usually consisting of a glued in or expansion bolt to which a hanger is permanently fixed (allowing passing climbers to clip a carabiner to the bolt). Bolts are used for protection in sport climbing and to make progress upward in aid climbing.
External links
Picture of Petzl brand bolt and hanger (http://img.epinions.com/images/opti/1d/c6/Petzl_Coeur_Goujon_Stainless_Steel_Hanger_Bolt_Climbing-resized200.jpg)
