Page 623 - Bob Holtzman "The Field Guide to Knots How to Identify, Tie, and Untie Over 80 Essential Knots for Outdoor Pursuits"

5. Pull the bight tight to close up the round turns around the main rope. Pulling down on the free part of the
sling will cause it to grip the main rope. With load off the sling, the round turns can be slid up or down the
main rope.

Uses: climbing; handholds, tie-offs or clip-on points; whitewater rescue; purchase on an anchor rope

Pros: quick, easy; secure in most situations
Cons: only secure under load; can slip if wet or icy

Untying: With load off, pull the bight through the crossing part, pull it

around the anchoring rope or pole, then pull it through a second time.

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