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 referred to as a Hercules knot. The knot is formed by tying an overhand knot and then a right-handed overhand knot. A common mnemonic for this procedure is right over left, left over right, 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 is at least 4,000 years old, the name reef knot dates from at least 1794 and originates from its common use to reef sails, 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 and it is specifically this behavior which makes the knot unsafe for connecting two ropes together. The name square knot is found in Danas 1841 maritime compendium A Seamans Friend, 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, not really a double slipped reef knot. The reef knot is used to tie the two ends of a line together such that they will secure something, for example a bundle of objects. In addition to being used by sailors for reefing and furling sails, 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 and is used extensively in medicine. In his Natural History, Pliny relates the belief that wounds heal more quickly when bound with a Hercules knot and it has also been used since ancient times to tie belts and sashes. A modern use in this manner includes tying the obi of a martial arts keikogi, with both ends tucked 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 forms a handle when tied in two twisted edges of the bag. The reef knot figures prominently in Scouting worldwide and it is included in the international membership badge and many scouting awards. In the Boy Scouts of America demonstrating the proper tying of the knot is a requirement for all boys joining the program. In Pioneering, it is used as a binding knot to finish off specialized lashing and whipping knots
The reef knot can capsize (spill) when one of the free ends is pulled outward.
Image: Egypte louvre 279 couple detail reef knot
Image: Ancient Greek jewelry Pontika (Ukraina) 300 b C