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In navigation, a knot is a unit of speed: one knot is one nautical mile per hour = 1.852 km/h = 0.514 m/s.

In many sailing ships, speed was measured by casting the log from the stern. The log was relatively immobile, and attached by line to a reel. Knots placed at a distance of 47 feet 3 inches passed through a sailor's fingers, while another used a 28-second sandglass to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation.

Ship speeds are usually reported in knots to this day.

See also Conversion Calculator for Units of SPEED (http://www.ex.ac.uk/cimt/dictunit/ccspeed.htm)

A knot is a method for fastening or securing linear material such as rope by tying or interweaving. It may consist of a length of one or more segments of rope, cord, twine[?], string, strap[?] or even chain interwoven so as to create in the line the ability to bind to itself or to some other object - the "load". Some knots are well adapted to bind to particular objects such as another rope, cleat[?], ring, stake or to constrict an object. Decorative knots usually bind to themselves to produce attractive patterns.

For a list of knots (approx. 300) see: List of knots.

Knots have been the subject of interest both for their ancient origins, common use or their mathematical implications, see knot theory.

Knots are essential in many industrial, work, home or recreational activities. Even simple activities such as running a load from the hardware store to home can result in disaster if a clumsy twist in a cord passes for a knot. Truckers need to tie down a load and will use a Trucker's hitch, gaining a 2-to-1 mechanical advantage. Are you spelunking, having foolishly but voluntarily buried yourself pre-maturely under millions of tons of rock? What ever the activity, on the water sailing or on a cliff-side rock climbing. Learning well tested knots prior to some hazardous activity introduces a critical measure of safety. Besides safety, using the appropriate knot can also save having to cut a line unnecessarily.

The list of knots is extensive but there are some general properties common to the various knot categories. For example, loop knots share the attribute of having some kind of an anchor point constructed on the standing end (such as a loop or overhand knot) into which the working end is easily hitched to using a round turn[?]). An example of this is the bowline. Constricting knots often rely on friction to cinch down tight on loose bundles. An example would be the clove hitch.

Some useful terms pertinent to the making of knots:

standing end
The end of the rope not involved in making the knot, often shown as unfinished.
standing part
Section of line between knot and the standing end.
working end
The active end of a line used in making the knot.
working part
Section of line between knot and the working end.
bitter end
More a ropeworker's term than a knot term, the reference is to the end of a rope that is tied off, hence the expression "to the bitter end". A bitt is a metal block with a crosspin used for tying lines to, found on docks.
The center part of a length of rope, string, or yarn (c.f., knitting and knitting needle) as opposed to the ends. The definition changes depending on whether the definite or indefinite article is used

  • "The bight" is any portion of the rope, string, or yarn between its two ends.

  • "A bight" is a U-shaped loop used in making a knot or stitch. Many knots, such as the bowline can be tied in either the end or the bight.

A full circle formed by passing the working end over itself.
Two crossing points created by an extra twist in a loop.

Knots may span multiple categories:

A knot uniting two lines, or two parts of the same line, usually at the end of each line, list of bend knots.
A knot that restricts object(s) by making multiple winds, list of binding knots.
Knots used tie up lines for storage, list of coil knots.
A complex knot exhibiting repeating patterns often constructed around and enhancing an object, list of decrorative knots[?]
A knot tied to a post, cable, ring, or spar, list of hitch knots.
A knot used to hold (usually) poles together, list of lashing knots[?]
A knot used to create a closed circle in a line, list of loop knots.
Knot tied with a hitch around one of its parts, contrasted. with a loop, which is closed with a bend. A noose can be closed, a loop remains the same size, list of noose knots[?].
A number of lines interweaved in a simple regular pattern, list of plait knots[?].
A knot used to hold two lines or two parts of the same line together, list of seizing knots.
A number of lines interweaved in a complex pattern, list of sennit knots.
A knot tied to hold a line through a hole, list of stopper knots[?].
A binding knot used to prevent another line from fray, list of whipping knots.

Some knots have multiple names. For example the overhand knot is also known as the thumb knot. The figure-of-eight knot is also known as the savoy knot or the flemish knot. All three are the same knot.

Useful references:

The Ashley Book of Knots
Ashley, Clifford W.
Clifford W. Ashley
Faber and Faber,London & Boston.
ISBN 0-385-04025-3

All The Knots You Need
R.S. Lee
Algrove Publishing
ISBN 0-921335-47-4

Knots & Splices
Cyrus L. Day
International Marine/McGraw-Hill Companies
ISBN 0-87742-252-4

The Ultimate Encyclopedia of Knots & Ropework
Geoffrey Budworth
Prospero Books, a division of Chapters Inc.
Annes Publishing Limited 1999
ISBN 1-55267-986-1

The Klutz Book of Knots
John Cassidy
Klutz Press, Palo Alto, California 1985
ISBN 0-932592-10-4

In knot theory, a knot is an embedding of a circle in 3-D space, considered up to deformations (isotopies). This is basically equivalent to a conventional knot with the ends of the string joined together to prevent it from becoming undone. In higher dimensions, circles are unknotted anyway, so one considers embeddings of spheres and hyperspheres, always in codimension 2.

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