A Prusik is a friction hitch or knot used to attach a loop of cord around a rope, applied in climbing, canyoneering, mountaineering, caving, rope rescue, ziplining, and by arborists. The term Prusik is a name for both the loops of cord and the hitch, and the verb is "to prusik". More casually, the term is used for any friction hitch that grabs a rope. The word is often misspelled as Prussik, Prussick or Prussic, as it is a homophone with the term prussic acid.
The Prusik hitch is named after the Austrian mountaineer Karl Prusik. It was shown in a 1931 Austrian mountaineering manual for rope ascending. It was used on several mountaineering routes of the era to ascend the final summit, where a rope could be thrown over the top and anchored so that climbers could attain the summit by prusiking up the other side of the rope.
A prusik made from cord does little or no damage to the rope it is attached to, although some mechanical prusiks can cause damage if the device slips during climbing.
Climbers carry Prusik cords for emergency use. Prusiks are fast to tie on a rope, and with practice can be placed with one hand. The loops of cord can be used as slings.
- Prusiks will work around two ropes, even two ropes of different diameters.
- Prusiks provide a strong attachment that will not damage or break the rope, and so are used in some rope-rescue techniques.
- Prusiks are used in hauling systems where rope-grabs are needed, and where mechanical rope-grabs are not available.
- Prusiks are unlikely to damage the main rope. A prusik which is overloaded will initially slip, causing no damage. If loaded to great excess, the worst result is that it slides until the heat of friction causes physical failure of the prusik cord.
- Prusik hitches work in both directions. Traditional Prusiks will grab when pulled by the tail, and will slide either way when pushed by the barrel.
- Prusiks are ineffective upon frozen wet ropes. This is due to the necessity of friction for the Prusik to function.
- After being put under a great deal of weight, the Prusik can be difficult to untie. This varies, depending on the relative diameter of the ropes.