A bend is a type of knot used to unite two lengths of rope, or two parts of the same rope. Bends are used in a variety of situations, including climbing, sailing, and securing loads. They are classified based on their ability to be tightened or released, their resistance to slipping, and their strength. Some common types include the sheet bend, the double fisherman's knot, and the double figure-eight bend. Bends allow the combined ropes to support weight or transmit force.
The common reef knot (square knot) is sometimes mistakenly tied as a bend. When used as a bend rather than a binding knot, the reef knot will capsize under sufficient tension. For this reason, the reef knot is insecure as a bend and as such is not listed as one.