Page 619 - Bob Holtzman "The Field Guide to Knots How to Identify, Tie, and Untie Over 80 Essential Knots for Outdoor Pursuits"

85. Prusik Knot

Climbers use the Prusik Knot to create moveable tie-off points on a vertical

climbing rope. Tied with a sling around the main climbing rope, it can be
easily slid up or down to reposition a carabiner or serve as a hand-or foot-
hold. The sling grasps the climbing rope only when load is applied up or
down. The rope of the sling should be no more than half the diameter of
the main rope.

Instructions

1. Make a bight in the sling, pass it behind the main rope, and pass the rest of the sling through the bight,
forming a loose Cow Hitch.

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