Butterfly knot

Butterfly Loop
A butterfly loop with a carabiner.
Names	Butterfly Loop, Alpine Butterfly Knot, Butterfly Knot, Lineman's Loop, Lineman's Rider
Category	Loop
Related	Alpine butterfly bend, Farmer's loop, Artillery loop, Span loop
Releasing	Non-jamming
Typical use	Fixed loop on the bight. Isolating a worn section of rope.
ABoK	#331, #532,#1053
Instructions	[1]

The butterfly loop, also known as lineman's loop, butterfly knot, alpine butterfly knot and lineman's rider, is a knot 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 a distinct advantage when working with long climbing ropes. The butterfly loop is an excellent mid-line rigging knot; it handles multi-directional loading well and has a symmetrical shape that makes it easy to inspect. In a climbing context it is also useful for traverse lines, some anchors, shortening rope slings, and for isolating damaged sections of rope.

The earliest known presentation of the knot was in A.A. Burger's 1914 work Rope and Its Uses, included in an agricultural extension bulletin from what is now Iowa State University. Burger called the knot a lineman's rider stating it was often used by "linemen and especially telephone men". The knot's security and ability to withstand tension in any direction are both discussed.

The knot's association with mountaineering—and with butterflies—originates from a 1928 article in Alpine Journal by C.E.I. Wright and J.E. Magowan. The authors claim to have developed the butterfly noose themselves while attempting to improve the selection of knots available to climbers. The name is "so styled on the basis of a more or less fanciful resemblance imagined in the form of the knot." In the second part of the article they express dissatisfaction regarding their earlier use of the word "noose," since the knot is non-collapsing, and refer to the knot as butterfly loop or simply butterfly. Wright and Magowan call the butterfly loop "new," along with several other of their knots, in the sense they were unable to identify any earlier record of them. However, they prudently added that it "might be rash to claim they have never been used before."