Expansion bolts like those used in construction,tapped into holes drilled in the rock (usually 3/8" diameter by about 3" deep) to protect climbs where there are no cracks for other types of protection. A special “hanger” is attached to the bolt, so the rope can be clipped to it with a carabiner. Bolts are permanent, or “fixed,” pieces of protection. They are placed only by the first person to do a climb and are used by all subsequent parties.