Reef knot

Last updated
Reef knot
Square knot.svg
NamesReef knot, Square knot, Hercules knot, Double knot, brother hood knot
Category Binding
Origin Ancient
Related Thief knot, Granny knot, Grief knot, Surgeon's knot, Shoelace knot
Releasing Jamming
Typical useJoining two ends of a single line to bind around an object.
CaveatNot secure as a bend. Spills easily if one of the free ends is pulled outward. Does not hold well if the two lines are not the same thickness.
ABoK #74, #75, #460, #1204, #1402, #2096, #2573, #2574, #2577, #2580

The reef knot, or square knot, is an ancient and simple binding knot used to secure a rope or line around an object. It is sometimes also referred to as a Hercules knot. The knot is formed by tying a left-handed overhand knot and then a right-handed overhand knot, or vice versa. A common mnemonic for this procedure is "right over left; left over right", which is often appended with the rhyming suffix "... makes a knot both tidy and tight". Two consecutive overhands of the same handedness will make a granny knot. The working ends of the reef knot must emerge both at the top or both at the bottom, otherwise a thief knot results.


The reef knot or square knot consists of two half knots, one left and one right, one being tied on top of the other, and either being tied first...The reef knot is unique in that it may be tied and tightened with both ends. It is universally used for parcels, rolls and bundles. At sea it is always employed in reefing and furling sails and stopping clothes for drying. But under no circumstances should it ever be tied as a bend, for if tied with two ends of unequal size, or if one end is stiffer or smoother than the other, the knot is almost bound to spill. Except for its true purpose of binding it is a knot to be shunned.

The reef knot is not recommended for tying two ropes together, because of the potential instability of the knot; something that has resulted in many deaths (see Misuse as a bend).


The reef knot is at least 4,000 years old. The name "reef knot" dates from at least 1794 [2] and originates from its common use to reef sails, [3] [4] that is to tie part of the sail down to decrease its effective surface area in strong winds. To release the knot a sailor could collapse it with a pull of one hand; the sail's weight would make the collapsed knot come apart. It is specifically this behavior which makes the knot unsafe for connecting two ropes together. [5]

The name "square knot" is found in Dana's 1841 maritime compendium A Seaman's Friend, which also gives "reef knot" as an alternative name. [6] [7]

The name square knot is often used for the unslipped version of reef knot. Reef knot itself then is understood as the single slipped version, while the name shoelace knot is to indicate double slipped version. Sometimes the name bowtie also may be used to indicate a double slipped version, but tying a bowtie is usually performed on flat material, and involves a slip knot of one end holding a bight of the other end i.e. not really a double slipped reef knot. The name "Square knot" is also used for completely different other knots such as the mathematical concept of square knot, or friendship knot; this last one earns the name by being flat and drawing a square on one face (and a cross on the other face).


The reef knot is used to tie the two ends of a single rope pieces together such that they will secure something, for example a bundle of objects, that is unlikely to move much. In addition to being used by sailors for reefing and furling sails, it is also one of the key knots of macrame textiles. [8]

The knot lies flat when made with cloth and has been used for tying bandages for millennia. As a binding knot it was known to the ancient Greeks as the Hercules knot (Herakleotikon hamma) and is still used extensively in medicine. [9] In his Natural History , Pliny relates the belief that wounds heal more quickly when bound with a Hercules knot. [10]

It has also been used since ancient times to tie belts and sashes. A modern use in this manner includes tying the obi (or belt) of a martial arts keikogi.

With both ends tucked (slipped) it becomes a good way to tie shoelaces, whilst the non-slipped version is useful for shoelaces that are excessively short. It is appropriate for tying plastic garbage or trash bags, as the knot forms a handle when tied in two twisted edges of the bag.

The reef knot figures prominently in Scouting worldwide. It is included in the international membership badge [11] and many scouting awards. [12] In the Boy Scouts of America demonstrating the proper tying of the square knot is a requirement for all boys joining the program. [13] In Pioneering (Scouting), it is commonly used as a binding knot to finish off specialized lashing (ropework) and whipping knots. [14] However, it is an insecure knot, unstable when jiggled, and is not suitable for supporting weight.

A surgeon's variation, used where a third hand is unavailable, is made with two or three twists of the ropes on bottom, and sometimes on top, instead of just one.

Misuse as a bend

The reef knot can capsize (spill) when one of the free ends is pulled outward. Capsizereefknot111.jpg
The reef knot can capsize (spill) when one of the free ends is pulled outward.

The reef knot's familiarity, ease of tying, and visually appealing symmetry conceal its weakness. The International Guild of Knot Tyers warns that this knot should never be used to bend two ropes together. [15] A proper bend knot, for instance a sheet bend or double fisherman's knot, should be used instead. Knotting authority Clifford Ashley claimed that misused reef knots have caused more deaths and injuries than all other knots combined. [16] Further, it is easily confused with the granny knot, which is a very poor knot.

Physical analysis

An approximate physical analysis [17] predicts that a reef knot will hold if , where μ is the relevant coefficient of friction. This inequality holds if . Experiments show that the critical value of μ is actually somewhat lower. [18]


See also

Notes and references

  1. Ashley, Clifford W. (1944). The Ashley Book of Knots, p.220. Doubleday. ISBN   0-385-04025-3.
  2. David Steel (1794), The Elements and Practice of Rigging and Seamanship, London: David Steel, p. 183
  3. Lever, Darcy (1998) [1819], The Young Sea Officer's Sheet Anchor (2nd ed.), Mineola, NY: Dover Publications, p. 83, ISBN   978-0-486-40220-8
  4. Cyrus Lawrence Day (1986), The Art of Knotting and Splicing (4th ed.), Annapolis: Naval Institute Press, p. 42
  5. Ashley, Clifford W. (1944), The Ashley Book of Knots, New York: Doubleday, p. 258, ISBN   978-0-385-04025-9
  6. Ashley, p. 220.
  7. Richard Henry Dana Jr. (1997) [1879], The Seaman's Friend: A Treatise on Practical Seamanship (14th revised and corrected ed.), Mineola, NY: Dover, p. 49, ISBN   0-486-29918-X
  8. Ashley, pp. 399-400.
  9. Hage, J. Joris (April 2008), "Heraklas on Knots: Sixteen Surgical Nooses and Knots from the First Century A.D.", World Journal of Surgery, 32 (4), pp. 648–655, doi:10.1007/s00268-007-9359-x, PMID   18224483, S2CID   21340612
  10. Pliny the Elder, Bostock, John; Riley, H. T. (eds.), The Natural History, p. 28.17, retrieved 2009-08-23
  11. See File:World Scout Emblem 1955.svg for an image of the emblem.
  12. Square Knots - Meaning and Placement , retrieved 2009-08-17
  13. Boy Scouts of America, Boy Scout Joining Requirements , retrieved 2009-08-23
  14. "Foolproof Way to ALWAYS Tie a Square Knot Right". Retrieved 2013-06-17.
  15. International Guild of Knot Tyers, Sea Cadet Knots , retrieved 2016-04-19
  16. Ashley, p. 18.
  17. Maddocks, J.H. and Keller, J. B., "Ropes in Equilibrium," SIAM J Appl. Math., 47 (1987), pp. 1185-1200
  18. Crowell, "The physics of knots,"

Related Research Articles

Knot Method of fastening or securing linear material

A knot is an intentional complication in cordage which may be practical or decorative, or both. Practical knots are classified by function, including hitches, bends, loop knots, and splices: a hitch fastens a rope to another object; a bend fastens two ends of a rope to each another; a loop knot is any knot creating a loop, and splice denotes any multi-strand knot, including bends and loops. A knot may also refer, in the strictest sense, to a stopper or knob at the end of a rope to keep that end from slipping through a grommet or eye. Knots have excited interest since ancient times for their practical uses, as well as their topological intricacy, studied in the area of mathematics known as knot theory.

Overhand knot

The overhand knot, also known as a a knot and half knot, is one of the most fundamental knots, and it forms the basis of many others, including the simple noose, overhand loop, angler's loop, reef knot, fisherman's knot, and water knot. The overhand knot is a stopper, especially when used alone, and hence it is very secure, to the point of jamming badly. It should be used if the knot is intended to be permanent. It is often used to prevent the end of a rope from unraveling. An overhand knot becomes a trefoil knot, a true knot in the mathematical sense, by joining the ends.

Granny knot

The granny knot is a binding knot, used to secure a rope or line around an object. It is considered inferior to the reef knot, which it superficially resembles. Neither of these knots should be used as a bend knot for attaching two ropes together.

The granny knot is also called the false, lubber's, calf, and booby knot. Patterson's Nautical Encyclopedia calls it "old granny knot" and Sir Edwin Arnold calls it the "common or garden knot." The name granny is given in Vocabulary of Sea Phrases and Roding pictures the knot in 1795.

The granny consists of two identical half knots, one tied on top of the other. It has but one practical purpose that I know of and that is to serve as a surgeon's knot. Formerly it was employed for tying up parcels in five-and-ten-cent stores, but the practice was given up and paper bags substituted as they were found to be simpler.

Thief knot Type of knot

The thief knot resembles the reef knot except that the free, or bitter ends are on opposite sides. It is said that sailors would secure their belongings in a ditty bag using the thief knot, often with the ends hidden. If another sailor went through the bag, the odds were high the thief would tie the bag back using the more common reef knot, revealing the tampering, hence the name. It is difficult to tie by mistake, unlike the granny knot.

Figure-eight knot Type of stopper knot used in sailing and climbing

The figure-eight knot or figure-of-eight knot is a type of stopper knot. It is very important in both sailing and rock climbing as a method of stopping ropes from running out of retaining devices. Like the overhand knot, which will jam under strain, often requiring the rope to be cut, the figure-of-eight will also jam, but is usually more easily undone than the overhand knot.

The figure-eight or figure-of-eight knot is also called the Flemish knot. The name figure-of-eight knot appears in Lever's Sheet Anchor; or, a Key to Rigging. The word "of" is nowadays usually omitted. The knot is the sailor's common single-strand stopper knot and is tied in the ends of tackle falls and running rigging, unless the latter is fitted with monkey's tails. It is used about ship wherever a temporary stopper knot is required. The figure-eight is much easier to untie than the overhand, it does not have the same tendency to jam and so injure the fiber, and is larger, stronger, and equally secure.

A whipping knot or whipping is a binding of marline twine or whipcord around the end of a rope to prevent its natural tendency to fray.

Grief knot

A grief knot is a knot which combines the features of a granny knot and a thief knot, producing a result which is not generally useful for working purposes. The word grief does not carry its usual meaning but is a portmanteau of granny and thief.

Hunters bend

Hunter's bend is a knot used to join two lines. It consists of interlocking overhand knots, and can jam under moderate strain. It is topologically similar to the Zeppelin bend.


Shoelaces, also called shoestrings or bootlaces, are a system commonly used to secure shoes, boots, and other footwear. They typically consist of a pair of strings or cords, one for each shoe, finished off at both ends with stiff sections, known as aglets. Each shoelace typically passes through a series of holes, eyelets, loops or hooks on either side of the shoe. Loosening the lacing allows the shoe to open wide enough for the foot to be inserted or removed. Tightening the lacing and tying off the ends secures the foot firmly within the shoe. The laces can be tied in different shapes, most commonly a simple bow.

Sheet bend

The sheet bend is a bend. It is practical for joining lines of different diameter or rigidity.

Stopper knot

A stopper knot is a knot that creates a fixed thicker point on an otherwise-uniform thickness rope for the purpose of preventing the rope, at that point, from slipping through a narrow passage, such as a hole in a block. To pass a rope through a block, or hole, is to reeve it. To pull it out is to unreeve it. Stopper knots prevent the rope from unreeving on its own.

Half hitch

The half hitch is a simple overhand knot, where the working end of a line is brought over and under the standing part. Insecure on its own, it is a valuable component of a wide variety of useful and reliable hitches, bends, and knots.

Two half-hitches

Two half-hitches is a type of knot, specifically a binding knot or hitch knot. One variety consists of an overhand knot tied around a post, followed by a half-hitch. This knot is less often referred to as a clove hitch over itself, double half-hitch, or full-hitch.

Two half hitches is the commonest of all hitches for mooring in particular and also for general utility. Steel gives the name in 1794. The difference between two half hitches and the clove hitch is that the former, after a single turn around a spar, is made fast around its own standing part, while the latter is tied directly around the spar.

Strangle knot

The strangle knot is a simple binding knot. Similar to the constrictor knot, it also features an overhand knot under a riding turn. A visible difference is that the ends emerge at the outside edges, rather than between the turns as for a constrictor. This knot is a rearranged double overhand knot and makes up each half of the double fisherman's knot.

The strangle knot starts with a round turn and the end is stuck under two parts. It may be used to tie up a roll.It can only be tied around a cylindrical shape. If required, a loop may be stuck instead of the end, which makes a slipped knot that is one of the best for tying up sacks and meal bags. With one or two additional turns the strangle knot makes an excellent temporary whipping for the end of a rope.

Bight (knot)

In knot tying, a bight is a curved section or slack part between the two ends of a rope, string, or yarn. A knot that can be tied using only the bight of a rope, without access to the ends, is described as in the bight. The term "bight" 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.

Shoelace knot

The shoelace knot, or bow knot, is commonly used for tying shoelaces and bow ties.

Double overhand noose

The double overhand noose is a very secure hitch knot. It might be used by cavers and canyoneers to bind a cow tail or a foot loop to a carabiner.[ [File:Noeud double gansé.jpg|thumb|Double overhand noose binding carabiners.]]