In technical climbing, a skyhook is a very small hook which gives hold on smallest protrusions, or watery and slippery grips. They are most often used for placements, often extremely marginal, in aid climbing, although they also feature in some extreme free routes. Additionally, the skyhook can be attached to the harness, thus allowing the climber to rest, or held in one or both hands to hold a grip.
In skateboarding and related sports, skyhooks are devices which serve as semi-open bindings. They are usually made of aluminium or hard plastic and are formed to cover the rider's boot, yet to allow him to easily free his feet from the hook. They may be screwed to the top of the board to facilitate jumping and enhance stability during a ride.