The climbing system is a general term for the techniques and equipment used by roped climbers to protect themselves against injury or death if they fall. It is the answer to the question sometimes asked by non-climbers, "How do they get the rope up there?"

It is usual to work in pairs, with one climbing and the other belaying (holding the rope, ready to anchor it if the climber falls). Long climbs are divided into shorter sections called pitches. Unless the climb starts from the ground (and even then, if the belayer is significantly lighter than the climber), the belayer is securely anchored to the rock at a belay

Both climbers attach the rope to their climbing harness. The leader climbs first, and attaches running belays to the rock. In traditional climbing these are temporary anchors, usually in the form of nuts or spring loaded camming devices placed in cracks in the rock. In sport climbing, these are usually bolts drilled and placed by another climber who has equipped the route.

The leader connects each anchor to a carabiner and clips the carabiner to the rope. If the leader falls off (and if the anchor is good and the belayer doesn't let the rope run) the leader won't fall much more than twice the distance to the last running belay. So by placing frequent running belays, the leader is protected against a fall.

If the leader falls, the belayer arrests the rope. This is achieved by running the rope through a belay device attached to the belayer's harness. The belay device runs the rope through a series of sharp curves that, when operated properly, greatly increase the friction and stop the rope running.

At the top of the pitch, the leader sets up a secure anchor or belay. Now the two climbers swap roles and the leader belays while the belayer (now called the second) climbs and removes the running belays. Both climbers are now at the top of the pitch with all their equipment. Note that the second is protected from above while climbing, but the leader is not. So being the leader is the more challenging and dangerous of the roles.