A heel hook is a foot technique that turns the leg into a third pulling limb. The climber places the back of the heel on a hold — typically above or beside the body — and contracts the hamstring and glute to pull, the same way an arm would pull on a hold. A well-placed heel hook can take so much weight off the upper body that some moves become almost effortless.
Heel hooks shine on overhangs, around aretes, on big slopers, and in roof climbing where the body needs to stay tight against the wall. The shoe matters: aggressive bouldering shoes with rubber wrapping the heel grip far better than gym rentals. The heel cup needs to fit snugly — a loose heel rolls off the hold under load.
Common mistakes include placing the heel too low (no leverage), allowing the hip to drop away from the wall (loses tension), or pulling with the calf instead of the hamstring (much weaker). The technique pairs naturally with toe hooks, where the top of the foot pulls instead. As climbing has trended towards more dynamic and gymnastic routes, the heel hook has become one of the most-used techniques in modern bouldering.