Gather these materials: A climbing harness, climbing rope, which, if you are in a climbing gym, will be hanging from the ceiling, a belay device, a locking carabiner,
First, you and your partner will need to put on your harnesses. Loosen the legloops and waist belt, then slide it over, making sure that no part of it is twisted.
Second, take one arm span of rope, then tie a figure eight knot on the long end. Tie this by making a loop, then going around the base, then through the loop again.
Put the rope through both hard points, and then thread it back through the figure eight, pulling out slack as you go.
Then, tie a double fisherman's by taking the loose end of the rope, looping it around both ropes two complete times, then pulling the end through both loops.
Unlock the carabiner, and attach it through the belay loop. Take a bite of rope, and push it through the belay device, then close the carabiner on the rope, the belay device, and the belay loop, then lock it.