Lead climbing

Lead climbing is a climbing technique used to ascend a route. This technique is predominantly used in rock climbing and involves a lead climber attaching themselves to a length of dynamic (elastic) climbing rope and ascending a route while periodically attaching protection (quickdraws or traditional protection) to the face of the route and clipping into it. The lead climber must have another person acting as a belayer. The belayer has multiple roles: holding the rope in the event of a fall, and paying out or taking up rope as the climber moves.

As lead climbing does not require a pre-placed anchor at the top of the route, it is often seen as less restricted than top roping. Also, because a lead climber does not have an anchor point above them while climbing, only the limbs and body of the climber are used to effect upward progress. Carabiners are only placed to catch the climber in the event of a fall.

When lead climbing, the lead climber or leader wears a harness tied to one end of a rope. The leader's partner provides the belay, paying out rope as needed, but ready to hold the rope tightly, usually with the aid of a belay device, to catch the leader in the event of a fall. The lead climber ascends the route, periodically placing protection for safety in the event of a fall. The protection can consist of pre-placed bolts and pitons, to which the climber clips quickdraws, or removable protection such as nuts and spring-loaded camming devices, which are carefully secured by the climber into cracks or other features. Distances between pieces of protection can range from three to forty feet or more, although most often the distance is between six and twelve feet.

At any point, the length of a fall will be at least twice that of the distance to the most recently placed protection. For example, if a leader is ten feet above the last piece of protection, a fall will be a minimum of twenty feet. Realistically, the fall would likely include several more feet due to rope elasticity and slack and give in the overall mechanical system. If a lead climber, starting from the ground, approaches twice the height of the last piece of protection, there is danger of a ground fall (more commonly referred to as "decking") in which the falling climber hits the ground before the rope goes tight.

...
Wikipedia