Prussik

A Prussik (or Prusik or Prussic) is a friction hitch used in climbing, canyoneering, caving, rope rescue and by arborists to grab a rope (sometimes referred to as a rope-grab). The term Prussik is used both for the knot, for the loops of cord, and for the action (to Prussik). More casually, the term is used for any friction hitch that can grab a rope.

The Prussik hitch is named for its inventor, Austrian mountaineer Dr. 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 block of a peak; where a rope could be thrown over the top, one side anchored, and climbers could attain the summit by prusiking up the other side of the rope.

Advantages of a Prussik hitch

Climbers carry Prusiks mainly for emergency use, as they are lighter than other options. Prussiks are fast to place on the rope, and with practice, can be placed with one hand. The loops of cord can be used as slings, and are thus multi-functional in a climbing environment.

Prussiks will work around two ropes, even two ropes of different diameters. Prussiks provide a high-strength and relatively fail-safe (i.e., they will slip before damaging the rope or breaking) attachment, and are used in some rope-rescue techniques. Prussiks are far less likely to damage the main rope as opposed to mechanical rope-grabs (or jumars).

Disadvantages of a Prussik hitch

For climbing a rope, Prussiks are slow and inefficient, as well as ineffective upon wet or frozen ropes. Mechanical devices (such as jumars) to grab the rope are available that are easier and faster to use, but heavier, more expensive and bulkier.

A Purcell Prussik is a related cord popular among cavers and rope-rescue people. A somewhat longer loop than the normal Prussik is used around the rope, then a second Prussik is used around the cord loop itself to form a foot loop. The foot loop is then easily adjusted in length and position.

A Prussik-Minding-Pulley is common in rope rescue. The rope to be pulled is passed through a pulley, and a Prussik is tied on the loaded side. When the rope is pulled, the Prussik rides against the pulley and the rope slides through it, but when the rope is relaxed, the Prussik slides away from the pulley and grabs the rope. Thus, the combination acts as a ratchet.

Tying the Prussik

The Prussik is tied by wrapping the Prussik loop around the rope a number of times (depending on the materials, but usually 3-5 times), and then back through itself, forming a barrel around the rope, with a tail hanging out the middle. When the tail is weighted the turns tighten around the main rope and grab. When weight is removed the loop can be slid along the rope by placing a hand directly on the barrel and pushing. The trick is, if it grabs well, then it is hard to slide along the rope. Breaking the Prussik free from the rope after it has been weighted can be difficult, and is easiest done by pushing the bow, being the loop of cord which runs from the top wrap, over the knot to the bottom wrap, along the tail a little. This loosens the grip of the hitch and makes movement easier.

Step 1.	Step 2.	Step 3.
Step 4.	Locked while holding tension.	Slides readily without tension.

Many materials may be used to tie a prussik. The webbing illustrated is one choice, but many find round cord to work better. In many instances, adding more wraps increases the grip.

A variation of the Prussik knot with additional friction.

Applications

In addition to being a useful rope-grab for rope-rescue applications, Prussiks are popular for:

• "Rappel Backup"/"Self-Belay Below The Device": A Prussik is placed below the descender and controlled with the brake hand. It acts as an automatic 'dead man's handle' should the climber be incapacitated or require the use of both hands. Careful setup of the rappel backup is critical, or it will not work. An AutoBloc knot is most widely used in this application. This technique is used by some rappellers, and not by others.

• "Rappel Backup"/"Self-Belay Above The Device": A Prussik is placed above the descender and controlled with the hand not being used as the brake hand. This configuration allows for easier and faster transition from rappeling to climbing the rope, but can also result in the Prussik locking tight as the amount of friction required to hold the load at that point is far higher than that experienced by a self-belay below the device.

• "Prussiking" or ascending the line: Two Prussiks used in tandem can be used to climb a fixed rope. One prussik is attached to the "belay loop" sewn onto the front of a harness and the other is attached to a longer length of cord reaching to one foot. With one loop attached to the rope above the other the climber can then stand up in the foot loop, slide the Prussik hitch of the waist loop further up the rope and then "sit" down on it. Once sitting, they can slide the foot loop up the rope and repeat the process.

• "Escaping the Belay": In a lead-climbing situation, should the belayed climber become incapacitated in a position where they cannot be safely lowered to the ground, the belayer must escape the belay in order to effect rescue. With the belay rope locked off with one hand, the belayer can tie a Prussik to the rope with the other hand, and transfer the load to a fixed anchor; thus allowing them to effect rescue or go get help.

Similar knots

• Lark's head or Cow hitch - a simpler form of the Prussik hitch.
• Cat's paw - this doesn't grab the rope.

External links

• Wikipedia page
• Prusik Knot at OZultimate.com canyoning with good pictures showing how it is tied.
• Prusik Knot used in Sailing for climbing a mast, with other notes.
• Many Varieties of Friction Hitches
• Discussion of Rappel Backups - Pros and Cons
• A detailed article, good pictures, several prusiks and ideas shown.