The Sheet Bend Knot is also known by the names Becket Bend, Weaver's Knot, and Weaver's Hitch. It is used to join two ropes of different diameters. It is related in structure to the bowline. The Sheet Bend is very fast to tie and is useful when joining two ropes of different diameters.
To tie the sheet bend, take the larger rope in one hand. Make a loop in this rope about three inches long and hold both ends of the loop in one hand. Next, take the smaller rope and thread it up the loop. Then wrap the smaller rope around the loop of the larger one going first round the short end. Then tuck it underneath where the smaller rope comes up through the larger rope's loop. Finally, pull the free end of the smaller rope tight to secure the knot.
Sheet Bend: Form a bight in the thicker rope (blue) and hold it in one hand. Pass the thinner rope (red) through the bight and behind the (blue) tail and standing ends in that order. Finally, tuck the smaller rope under itself to finish the knot.
Double Sheet Bend: When the ropes are markedly different in size, the tail of the smaller rope can be taken twice round the bight in the larger rope to create the double sheet bend.