Page 106 - Geoffrey Budworth, Jason Dalton "The Little Book of Incredibly Useful Knots"

Butterfly loop

This knot, also known as the alpine butterfly, is used to put a loop in a section of rope where

there will be tension along both standing ends. The butterfly does not greatly weaken the
strength of the rope, and is often used by mountaineers to attach a team of climbers along a
rope, for protection against a fall.

Start by taking a bight of rope and twisting it into a loop (1). Continue twisting in the same

direction to make a second loop above the first (2). Bring the top loop down below the twists (3).
Then feed the top of the bight up through the first small loop (4). Pull the slack out of the knot,
then pull on the standing ends to tighten (5).