Lead climbing is a climbing technique. The lead climber ascends with the rope passing through intermittent anchors that are below them, rather than through a top anchor, as in a top-roped climb. A partner belays from below the lead climber, by feeding out enough rope to allow upward progression without undue slack. As the leader progresses he or she clips the rope into, using a runner and carabiners, intermediate points of protection such as active cams, or passive protection such as nuts; this limits the length of a potential fall. The leader also may clip into pre-placed bolts. Indoor gyms might have short runners pre-attached to fixed anchor points in the wall.
Unlike top-rope climbing where the climber is always supported by an anchor located above the climber, lead climbing often has scenarios where the climber will be attached to a point under him or her. In these cases, if the climber were to fall, the distance fallen would be much greater than that of top-rope and this is one of the main reasons lead climbing can be dangerous. The fall factor is the ratio of the height a climbers falls and the length of rope available to absorb the fall. The higher the fall factor, the more force placed on the climber as the ropes decelerates them. The maximum fall factor is 2. It is often advised that climbers who are interested in lead climbing should learn from experienced climbers and participate in training sessions before actually lead climbing on their own.