A Prusik knot, named for its inventor Dr. Karl Prusik, an Austrian mountaineer in the 1920s, is a sliding friction knot or hitch that is used by climbers to ascend a fixed rope. The knot, tied with a loop of cord attached onto the rope, is clipped to the climber's harness and then pushed up the rope by the climber. When it is weighted by the climber, the knot grips the rope, allowing the climber to ascend upward.
Prusik knots have advantages and disadvantages:
- Usually used in pairs.
- Are easy to tie.
- Don’t damage the rop
- Can slide down as well as up the rope.
- Can be tied with either a thin cord or a nylon sling.
- Are ineffective on icy ropes.
- Are prone to tighten up after being weighted or loaded.
- Are commonly used in emergency situations such as escaping a belay after an accident or ascending the rope after falling into space below an overhang.
Prusik is also used as the verb “to Prusik” meaning to ascend a rope using a Prusik knot. Also “Prusiking” is the act of ascending a fixed rope with the knots.
The cords used to tie Prusik knots are usually called “Prusik slings.”