It is sometimes necessary to shorten a rope temporarily and not
desirable to cut it, and the sheep-shank knot solves the problem. It
is used by the sailors, who do not believe in cutting ropes. It will
stand a tremendous strain without slipping, but will loosen when held
slack, and can be untied by a quick jerk of the two outside ropes
forming the bights.
Begin by bending the rope to form two bights as in _A_, Fig. 64, carry
the single rope over at the top of the bend, then under to form a
half-hitch as in _B_. Do the same with the other single rope at the
bottom of the bend _C_, and draw both ends tight (_D_). With a little
practise this can be done very quickly. If the rope is to be permanently
shortened pass the ends through the first and second bights at the bend
as in _E_, and the knot will hold for any length of time.