Alpine butterfly

The Alpine butterfly knot is used to form a fixed loop in the middle of a rope.

Tied in the bight, it can be made in a rope without access to either of the ends; this is an advantage when working with long climbing ropes. The butterfly loop handles multi-directional loading well and has a symmetrical shape that makes it easy to inspect.

Uses

In a climbing context it is also useful for traverse lines, some anchors, shortening rope slings, and for isolating damaged sections of rope.

• The loop is used to attach to a climbing harness using carabiners.
• It can be used to isolate a worn section of rope, where the knot is tied such that the worn section is isolated in the loop (which of course does not have a carabiner nor bear any loads in this case). The loop portion is isolated when the other two legs are loaded,
• The butterfly can be tied as a Alpine butterfly bend with the ends emerging where the loop would be.

Tying

Errors in tying the butterfly loop can produce a similar looking but inferior knot, the so-called "false butterfly", which is prone to slipping.

Advantages

• Forms stable, secure loop after initial setting
• The knot to be loaded three ways; by each end of the main line and the loop
• Relatively non-jamming (more difficult if wet)
• Size of loop can be adjusted
• Can easily be tied one-handed
• Can be tied on a bight.

Disadvantages

• Difficult to tie around a solid ring or similar object,
• Improper tying can result in similar looking but inferior "false butterfly" knot,
• Works better with softer ropes.