Bight (knot)
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The term bight is used in knot tying to refer to any curved section, slack part, or loop between the two ends of a rope, string, or yarn.[1] An important concept, the term is used extensively in the description of knots and the discourse of knotting and related subjects.
A familiar practical use is finishing a knot by passing a bight, rather than the end, to make a slipped form of the knot which is more easily untied. The traditional bow knot used for tying shoelaces is simply a reef knot with the final overhand knot made with two bights instead of the ends.
The term is also used in a more specific way when describing Turk's head knots, indicating how many repetitions of braiding are made in the circuit of a given knot.[2]
[edit] In the bight
The phrase in the bight (or on a bight) means a bight of line is itself being used to make a knot. Specifically this means that the knot can be formed without access to the ends of the rope.[3] This can be an important property for knots used in situations where the ends of the rope are inaccessible, such as forming a fixed loop in the middle of a long climbing rope.
Many knots normally tied with an end also have a form which is tied in the bight, for instance the bowline and the bowline on a bight. In other cases a knot being tied in the bight is a matter of the method of tying rather than a difference in the completed form of the knot. For example the clove hitch can be made in the bight if it is being slipped over the end of a post but not if being cast onto a closed ring, which requires access to an end of the rope. Other knots, such as the overhand knot, cannot be tied in the bight without changing their final form.
[edit] Examples
 The blue rope (right) is half-hitched through and around a bight of the red rope (left) in this Sheet bend |
 The final tuck of this Slipped buntline hitch is made with a bight rather than the end, making it easier to release after tightening |
 In the tying of a marlinespike hitch a bight of the standing part is snagged through the loop |
 The bights, in the case of this 3-lead 10-bight Turk's head knot, are the scallops along the perimeter of the knot |
 The Alpine butterfly knot is a popular climbing knot which is tied in the bight and forms a reliable fixed loop |
 The Bowline on a bight forms two fixed loops in the middle of a rope |
 An Overhand knot tied in the bight results in an Overhand loop |
 A Figure-of-eight knot tied in the bight results in a Figure-of-eight loop |
