Abseiling is a single-rope method of lowering down off cliffs or mountain faces. The issue with abseiling is setting the rope so it is possible to get it off the face without damage due to friction. This is more technical than it sounds, as the rope is subject to extreme forces. Abseiling and mountaineering are dangerous and require high degrees of training and skill. Do not attempt any climbing or abseiling technique with only one article under your belt. Get properly trained to prevent injury or death.
Configure the rope anchors so you have a three-point sling system. Find two static points on the top of the cliff face, such as trees, rocks or large boulders. Set one nylon webbing sling to each static anchor and then connect the two slings with a third sling via two carabiners (metal D-clips). The result is an evenly shaped Y, with two points of the Y anchored to static objects and the third connecting the others with the carabiners.
Pass the abseil rope through a locking carabiner at the end of the sling connecting the two anchors. Give the centre sling a twist and then clip the locking carabiner into the twist, preventing any extra friction on the rope, carabiner and sling. Turn the locking carabiner's gate clockwise all the way and then back one-quarter turn for safety.
Pass both ends of the rope down the cliff so you have two even ends of the rope coming off the abseil anchor rigging.
Clip into the abseil rope via your harness, locking harness carabiner and abseil device. Execute your descent, or abseil.
On the ground, or cliff for the next pitch, step to the side of the rope at least 2 to 3 feet and then pull down on one end of the rope until the other side goes up and around the carabiner at the anchors.
Let the rope fall down, making sure to hold one end to prevent it from falling off the cliff, should you be cliffed out -- when on a ridge or ledge -- and ready to set another pitch. You sacrifice the slings and anchors, yet keep the crucial climbing rope.
Do not attempt this without proper training from a mountaineering professional or instructor.