Page 304 - Geoffrey Budworth, Jason Dalton "The Little Book of Incredibly Useful Knots"

Double Blackwall hitch

This centuries-old method of temporarily attaching a vegetable-fiber rope to the hook of a

crane is strong enough as long as the load remains constant, but is obviously insecure. It was a
method of hauling taut the standing rigging of sailing ships, but must never be used for hoisting
heavy weights or in situations where failure could result in injury, damage, or loss. It is

unsuitable for modern synthetic ropes.

Lay one end of the rope within the mouth of the hook, taking the working end around the hook’s
shank (1), and then around again, tucking it beneath its own standing part (2). This hitch will only
hold as long as there is pressure from the standing part on the loose end (3). It is debatable if the
second turn (which gives this knot its name) improves or impairs its friction.