Prussic

The Prussic is a knot commonly used to ascend a rope instead of a mechanical device (see ascender or SRT). It resists being moved when being pulled from the bite of the rope hanging off it, but it can be slid up the rope by pushing it up from the base of the knot. It can be tied at any point on the rope.

Get a loop of accesory cord (red) joined with either a Square Knot or Water Knot (pictured), then begin to loop it around the main line (black).

At this point, it should look like a Girth Hitch or a Lark's Head.

Take the bite of rope hanging off the Girth Hitch, and loop it around the main line again by fishing it through the loop created by the accesory cord on the other side of the rope. If you go back around the accesory cord, however (instead of going around the main line), you'll get what's called a Cat's Paw.

Tighten up the bite that you just pulled through. Notice that the knot can move easily when pressure is aplied to the knot itself, but it locks up when pulled from it's bite (as pictured below).

Because this knot stays in place because of the friction it aplies to the rope its connected to, mud can limit the effectiveness of the knot. That being said, it has been used so much in the caving community that ascending or jugging is sometimes refered to as "prussicing."

The stereotypical example of an ideal use for this knot is when a second falls off a ledge and can't pendulum back into place. They can use a prussic to help them get up the rope enough to go over the ledge.

Related Pages

• Caving
• Escaping The Belay
• Klemheist
• Knots
• Prusic
• Prusik
• Prussik