In rock climbing, an overhang is a type of route that leans back at an angle of over 90 degrees for part or all of the climb, and at its most severe can be a horizontal roof. Overhang climbs have existed throughout climbing, originally in aid climbing where mechanical devices were used to first scale them. They became more common in free climbing during the 1990s as sport climbers used new training methods that enabled them to climb routes that were continuously, and severely, overhanging. Overhangs also feature prominently in advanced bouldering and in competition climbing.