Sheet Bend (Becket Bend, Weaver's Knot or Weaver's Hitch)
The sheet bend is a bend, that is, a knot that joins two ropes together. Doubled, it is effective in binding lines of different diameter or rigidity securely together, although it has a tendency to work loose when not under load.
The sheet bend is related in structure to the bowline. It is very fast to tie, and along with the bowline and clove hitch is considered so essential it is knot NoS1 in the Ashley Book of Knots. It is a more secure replacement for the reef knot (square knot), especially in its doubled variety.
The "weaver's knot" takes its common name from its historic use in textile mills. Even in modern operations, weavers are taught to use this particular knot when correcting broken threads in the warp. In practice, weavers are taught to be able to tie the knot in as little time possible, with the mean average being no more than three to five seconds.