The history and uses of the reef knot

History:

The reef knot is at least between 4,000 and 9,000 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; 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.

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

Uses:

The reef knot is used to tie the two ends of a single line 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 macrametextiles.

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. In his Natural History, Plinyrelates the belief that wounds heal more quickly when bound with a "Hercules knot".

It has also been used since ancient times to tie belts and sashes. 

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 Scoutong worldwide. It is included in the international membership badge and many scouting awards. In the Boy Scouts of America demonstrating the proper tying of the square knot is a requirement for all boys joining the program.


for more information visit: 
http://www.wikihow.com/Tie-a-Reef-Knot
http://www.realknots.com/knots/reefk.htm
http://www.animatedknots.com/reef/index.php