thumb|right|300px|1. garn-knop 2. fallrepsknop 3. käringknop 4. taljerepsknop 5. ormhufvud 6. vantknop 7. pertkunta 8. överhandsknop 9. sjömansknop 10. halvslag om egen part
:''Denna artikel handlar om knop med betydelsen knut. Se också knop (enhet)''.

'''Knop''' eller '''knut''', från holländskans ''knoop'' som betyder "knut",  kallas anordning använd för att sammanfoga tågvirke, rep, linor, trådar etc., för att fästa dem vid något, eller för att bilda ögla. Ordet knop används främst av scouter eller i samband med båtar.

Ordet knop avsåg ursprungligen endast sådan som gjordes på repet eller dess kardeler så att en kula bildades. Alla andra knutar, till exempel för att fästa rep, sammanfoga rep eller bilda öglor, kallades '''stek''', från holländskans ''steek''.  Skillnaden är sedan länge utsuddad och bortglömd. Numera kan skillnaden istället sägas vara att ''knopar'' är knutar som man använder med medvetenhet om deras lämplighet för särskilda användningsområden medan ''knutar'' är knutar i största allmänhet.

== Historia ==
Knopar har i alla tider varit ett hjälpmedel och redskap för människan. Redan under den europeiska stenåldern 500 000 f.Kr använde man sig av knopar. Man använde sig av senor, vidjor och utskurna remsor från djurhudar för att fästa samman och hänga upp saker. Senare lärde sig människan att utvinna växtfiber och tillverka rep och i takt med att människan och material utvecklats, har knopslagarkonsten förfinats. Det är inte länge sedan gemene man använde sig av knopar i sitt vardagsliv. Vi använder fortfarande i viss utsträckning knoparna i det vardagliga livet, t ex när vi knyter skorna. Den vanligaste knopen är överhandsknopen, det vi kallar "knut". 

== Knoparna och sjöfarten ==
Knopar förknippas starkt med sjöfart. I dag är den kopplingen inte lika stark och naturlig som den var för hundra år sedan då det fortfarande var vanligt förekommande med segelfartyg, men knopar används fortfarande ombord på dagens moderna fartyg. 

Knopslagandet var som störst i början av 1800-talet. Sjömännen rekryterades i tidig ålder och få kunde läsa. På så sätt blev det naturligt för sjömännen att sysselsätta sig med handarbeten. Man använde det gamla uttjänade tågvirket från riggen. En duktig knopslagare värderades högt och ofta synades sjömannens sjömanssäck eller sjömanskista lika noggrant som sjömannen själv. Det var först i mitten av 1800-talet som sjönationerna blev medvetna om sina sjömän och drog igång projekt för att lära dem läsa. Samtidigt hade man i England börjat experimentera med ångdrivna fartygsmaskiner och propellern utvecklades. I Amerika höll man fast vid segelfartygen och lyckades under 50 år förfina skeppsbyggarkonsten mer än vad man dittills lyckats göra de senaste 4 000 åren. 

Till en början var klipperskeppen överlägsna ångfartygen, men allteftersom ångtekniken utvecklades och förfinades, fick segelfartygen se sig besegrade. Den här utvecklingen ledde till att besättningarna slimmades ombord på segelfartygen och att mycket av riggens tågvirke byttes mot vajer. På ångfartygen fanns en liten eller ingen rigg alls och på så sätt började knopslagartraditionen dö ut.

I takt med att fartygen blivit modernare har behovet av knopar minskat drastiskt. Ombord på ett modernt handelsfartyg använder man sig i huvudsak av tre knopar: skotsteken, pålsteken och halvslaget. Utöver det händer det att man taglar, samt splejsar ögon (Öglor). För stålwire, som är vanligt på moderna fartyg, används speciella knopar anpassade för wirens styvhet och glatta yta. Dessa är en kombination av traditionell knopteknik, med vars hjälp man tar upp huvuddelen av belastningen, och ibland moderna wirelås av metall, med vars hjälp man låser fast de obelastade tamparna. 

Ett annat stort användningsområde för knopar var knytning av fisknät och andra fiskeredskap.

== Hobbyanvändning ==
Förutom scouting och båtar används knopar inom flera andra fritidssysselsättningar exempelvis makrameknytning.

frame|right|Some knots: 1.&nbsp;[[rope splicing|Splice 2.&nbsp;Manrope&nbsp;knot 3.&nbsp;Granny&nbsp;knot 4.&nbsp;Rosebud&nbsp;stopper&nbsp;knot(?) 5.&nbsp;Matthew&nbsp;Walker's&nbsp;knot 6.&nbsp;Shroud&nbsp;knot 7.&nbsp;Turks&nbsp;head&nbsp;knot 8.&nbsp;Overhand&nbsp;knot, Figure-of-eight&nbsp;knot 9.&nbsp;Reef&nbsp;knot or Square&nbsp;knot 10.&nbsp;Two&nbsp;half&nbsp;hitches (see&nbsp;round&nbsp;turn&nbsp;and&nbsp;two&nbsp;half&nbsp;hitches)]]

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, string, webbing, twine, 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".  Knots have been the subject of interest both for their ancient origins, common use, and the mathematical implications of
knot&nbsp;theory.

==Usage==

There are a large variety of knots and each knot has specific properties and suitability for a range of tasks.  Some knots are well-adapted to attach to particular objects such as another rope, cleat, ring, or stake.  Other knots are made to bind or constrict around an object.  Decorative knots usually bind to themselves to produce attractive patterns.  Choosing the correct knot for the job at hand is one of the most fundamental aspects of using knots well. However, if memory is limited, three of the most useful knots are the bowline, the sheet bend, and the clove hitch.<ref>Cassidy 1985, ''The Klutz Book of Knots''</ref>

===Learning===
The number of books, websites, videos, and other resources available to those interested in learning about knots is a testament to the value they hold for humankind.  While some people possess an innate ability to look at a diagram or photo and tie the illustrated knot, for others the initial stages of learning are best accomplished by being shown knot tying methods by a person who already knows them.  Knot tying skills are often transmitted by scouts, climbers, cavers, rescue professionals, fishermen, and surgeons. After mastering a few basic knots, the diagrams and photos become easier to interpret and use to continue the learning process.   As more knots are learned, patterns begin to become evident in their structure and methods of tying.  The learning of knots rewards practice and patience.
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===Applications===

Knots are essential in many industrial, occupational, recreational, and domestic settings. 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 needing to tie down a load may use a spelunker from foolishly becoming buried under millions of tons of rock. Whatever the activity, such as sailing on the water or climbing on a cliff-side rock, learning well-tested knots prior to some hazardous activity introduces a critical measure of safety. In addition to safety, appropriate knots can prevent the necessity of cutting lines.

Knots can be applied in combination to produce complex objects such as netting.  In knits, crochets, weaves or felting.  Macramé can produce self-supporting three dimensional textile structures, as well as flat work, and is often used ornamentally or decoratively.

===Basic useful knots===
Some of the most useful everyday knots are the following. Most are both secure and easy to untie:

*For tying a loop in the end of a rope, as around your waist or to secure a ring or grommet: the bowline. 
*For tying the ends of two ropes together: the sheet bend works well even with two different ropes. This is just as easy to tie but much more secure than the square knot. If one rope is much thicker than the other, a double sheet bend is better. (Materials such as cables which are not easily tied may sometimes be joined by two interlocking bowlines instead.)
*The fisherman's knot is similar but easier to tie with cold, wet hands.
*For flat material such as (seat)belts, the grass bend is best. (However, this is a poor knot for tying ropes.)
*For tying a rope to a pole, the slipped variant is useful for quick release. 
*On square posts where the clove hitch is not secure, two half-hitches is good. It can be hard to untie, so the slipped variant may be useful.
*The Killeg hitch is a variant used for hoisting rocks and other odd shapes. 
*The rolling hitch is useful when you don't want a rope to slide up on down a pole, or when tying one rope to the middle of another.
*For a clothesline or other line that sags over time, the taut-line hitch can be ratcheted up to take out the slack.
*The trucker's hitch is useful for clinching down a load.
*The sheep shank is useful for taking slack out of the middle of a rope, but will only hold as long as there's strain on the rope. 
*The constrictor knot works well for making bundles or tying the neck of a sack. However, it is nearly impossible to untie once tightened, and will likely need to be cut with a knife. 
*The harness loop puts a secure loop in the middle of a rope when the ends aren't free.
*For climbing a rope, the Prusik knot allows you to make footholds out of loops of narrower rope which ratchet up the main rope. (The loop can be made by tying together the ends of a rope with a (double) sheet bend.)
*The diamond hitch works well for packing trail animals.
*The figure-of-eight knot stops the end of a rope from slipping through a hole or other tight spot.

==Properties==
===Strength===
Knots invariably weaken the rope they are made in.  When knotted rope is strained to its breaking point, it almost always fails in or near the knot, unless it is defective or damaged elsewhere.  The bending, crushing, and chafing forces that hold a knot in place also unevenly stress the rope fibers and ultimately lead to the reduction of strength.  The exact mechanisms that cause the weakening and failure are complex and are the subject of continued study.

The relative knot strength, also called '''knot efficiency''', is the breaking strength of a knotted rope as a proportion of the breaking strength of the rope without the knot.  There are many difficulties in determining an overall numeric knot efficiency for a given knot.  This is due to the many factors that can affect the results of a knot efficiency test: the type of style of rope, the size of rope, whether it is wet or dry, how the knot is dressed before loading, how rapidly the knot is loaded, whether the knot is repeatedly loaded, and so on.  With those limitations noted, most common knots have an efficiency between 40% and 80%.

While some rope splices can retain nearly the full strength of the rope when forming loops and bends, conventional knots are much more practical in most situations.  Thus the prudent knot user will always allow for a large safety margin in the strength of rope chosen for a task due to the weakening effects of knots, aging, damage, shock loading, etc.  In general, the '''safe working load''' is often specified as between 10% and 20% of the rated breaking strength of the rope being used.[http://www.boatsafe.com/marlinespike/safeload.htm]  For safety of life applications many other factors come into play which are beyond the current scope of this article.  Experienced practitioners should always be consulted before using ropes and knots when safety of life, limb, or property is involved.

===Security===

Even if the rope does not break, a knot may still fail to hold.  A knot which holds firm under a variety of adverse conditions is said to be more secure than one that does not.  The main ways knots fail to hold are:

==== Slipping ====
The tension from the load causes the rope to work back through the knot in the direction of the load.  If this continues far enough, the working end will pass into the knot and the knot unravels and fails.  This behavior can be worsened when the knot is repeatedly strained and let slack, dragged over rough terrain, or repeatedly impacted such as against a mast or flagpole.  

Even with secure knots, some slippage may occur as the knot is first put under real tension.  This can be dealt with by leaving plenty of rope at the working end outside of the knot and by dressing the knot cleanly and tightening it as fully as possible before loading.  In some cases the use of a stopper knot or, even better, a backup knot can prevent the working end from passing through the knot, but it is generally better to use a more secure knot if one is observed to slip.  In life critical uses backup knots are often added to already secure knots in order to maximize safety.

==== Capsizing ====
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Capsizing (or spilling) a knot is changing its form, rearranging its parts, usually by pulling on specific ends in specific  ways.  Some knots when used in an inappropriate way tend to capsize easily or even spontaneously.  Often the capsized form of the knot offers little resistance to slipping or unraveling.  For an excellent example of a knot that capsizes dangerously, see the discussion of the reef knot used as a bend.  

Sometimes a knot is intentionally capsized as a method of tying another knot, such as the "lightning method" of tying a Bowline.  Some knots, such as the Carrick Bend, are generally tied in one form and then capsized to attain a stronger or more stable form.