How to Tie a Purcell Prusik Loop for Rock Climbing

The Purcell Prusik loop (sometimes spelled Prussik) is a friction hitch and adjustable loop tied with a Prusik knot and either a figure-eight knot or double fisherman’s knot. The hitch can serve as an adjustable tether or as a personal anchor system during ascent and descent and is often used by search-and-rescue personnel in a knot system called the Purcell Prusik System.

Other common climbing knots include the bowline knot, alpine butterfly, clove hitch, girth hitch, and Klemheist knot.

The Purcell Prusik system is a collection of tied knots that search-and-rescue personnel or other climbers use for ascending, descending, tying into an anchor point, or working with a suspended stretcher (called a litter). The Purcell Prusik system consists of three knots made from accessory cords of varying lengths to allow for comfortable climbs without the ropes getting in each other’s way:

• Medium foot Prusik: The medium foot loop is a Purcell Prusik knot that should reach from the rescuer’s boot to their groin and is the first to be attached to the mainline in the system. Experts recommend placing the medium loop onto the mainline first so the hanging rope doesn’t interfere with the tying of the other loops.
• Long foot Prusik: The long foot loop is a Purcell Prusik knot that should reach from the rescuer’s boot to their chest and is the second to be attached to the mainline climbing rope in the system.
• Short harness Prusik: The short harness is a Prusik loop long enough to let the rescuer bypass a brake bar rack (or another descent device) when an ascender switches over from a descending rappel system. The harness is the last to be attached to the mainline in the system.

Purcell Prusik loops are extremely versatile and useful in several situations:

1. 1. Search and rescue: The most common use of Purcell Prusik loops is in rope rescue operations due to their flexibility. They can serve in ascents and descents (either free-hanging or sloping) as adjustable tethers, tie into an anchor point, or attach to a litter, or suspended stretcher.
2. 2. Rock climbing or mountaineering: Purcell Prusiks are widespread in recreational climbing because they’re an adjustable and easy-to-make option that allows climbers to ascend and descend safely. Prusiks are also a handy knot to have on hand for emergency anchoring or to absorb the shock from a fall.
3. 3. Tree climbing: Less commonly, arborists use Purcell Prusik knots as a safe way to ascend or descend trees or to serve as an adjustable tether.

Here’s how to tie a Purcell Prusik loop:

1. 1. Choose your rope. The best Purcell Prusik cord is strong enough to support a shock load but thin enough that it’s not too bulky or heavy—most climbers opt for cords ranging from five to eight millimeters.
2. 2. Lay out your rope. Make an S-shape with your nylon cord, then compress it horizontally so you can easily hold all three layers of the rope with one hand. Adjust the length of each end so that the top layer only reaches about the middle of the length, and the bottom layer falls several inches short of the left edge.
3. 3. Tie a figure-eight knot. Grip the rope in a spot on the length that has all three pieces of the rope. Tie a figure-eight knot on the bight—the middle part between each end of the rope—leaving two tails. Dress the knot to ensure it’s tight and even.
4. 4. Tie a Prusik knot. On the right end of your rope, tie a Prusik hitch onto itself, using the left end of the rope as the main rope. Dress the knot to ensure it’s tight and even.

The Purcell Prusik loop has several advantages:

1. 1. Adjustable: The Purcell Prusik loop’s adjustability is a major feature, allowing the climber to shorten or lengthen the rope, even under a load.
2. 2. Flexible: The Purcell Prusik loop can be used in many situations, including ascent or descent—whether in free-hanging or sloping environments—with carabiners, tying into an anchor point, and working with a litter, or suspended stretcher.
3. 3. Shock-absorbant: When subject to a shock load (for instance, if the climber were to slip), the Purcell Prusik loop slips slightly before locking into place—this slip absorbs shock from the fall and can prevent additional damage to the climber or equipment.
4. 4. Relatively lightweight: Purcell Prusik loops are more lightweight than metal-based ascent, descent, or tether equipment, so they’re easier to have on hand in any given situation.

The Purcell Prusik loop has a few disadvantages:

1. 1. Bulkiness: Purcell Prusik loops are bulkier than other lanyard options, like daisy chains, so they may take up more space in your pack.
2. 2. Weight: Purcell Prusik loops can be heavier than other rope-based tether and climbing equipment, especially when tied with a thicker nylon cord.
3. 3. Tendency to slip: Purcell Prusik loops are supposed to slip slightly under shock load pressures (which gives them their shock-absorbing characteristics)—so it’s not a good choice if you’re looking for a static, non-slip knot.

Climbing is a high-impact activity with an elevated risk of serious injury. Practice, proper guidance, and extensive safety precautions are essential when attempting a climbing pursuit. This article is for educational and informational purposes only, and is not a substitute for professional instruction or guidance.

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