Tying a reef knot
The Boy Scout instructions for this knot are: right-over-left and under; left-over-right and through.
More formal, tie a left-handed overhand knot and then a right-handed overhand knot or vice versa.
Do not tie two knots of the same handedness. That makes a Granny knot.
This knot is the first knot most Boy Scouts learn, and in fact mastery of the knot is listed among the joining requirements in several countries.
The Reef knot is only useful in basic applications. It should be used to bind small laces or ropes together, provided not too much force is applied on it, but should not be used as a bend knot. It is easily tied and since it won't jam, also easily untied. It is used to tie packages, and as a base for the shoe-bow. Sailors used it for binding rolled sails or better reefed sails.
If you pull on one end, at right-angles to the knot, it will loosen and invert (turning into a lark's head knot), hence its original purpose: it secured the furled-in sails, and is easily undone one-handedly by a sailor who is holding on with the other hand. The weight of the sail would drag the lark's head undone.
A number of knotting guides have voted this knot "the worst knot", and noted that more deaths and injuries have been caused by its misuse than all other knots combined. Its symmetry and initial feel of security have led to it having a wide and undeserved reputation as a secure knot, which it certainly is not, especially if the ropes are of differing sizes or materials, or if the rope is likely to be bumped.
The International Guild of Knot Tyers (IGKT) warns that this knot should never be used to bend two ropes together even though many scout troops, and other organisations around the world, insist on teaching it for this very purpose. It is likely that this is the cause of most of the deaths referred to above.
- Square knot (American)
- Platte knoop (Dutch)