This is the basic fishing knot. The half-barrel knot is the simplest way to tie nylon or fluorocarbon with an eye. The key to this knot is to moisten the knot before tightening it, very gradually, until the turns are joined. Tightening too quickly without moistening heats up and twists the monofilament just before the knot. This causes the yarn to become brittle.
The simplicity of this knot means you can tie it with your eyes closed. The finer the thread, the greater the number of turns. For example, for trout, a 0.20 mm thread will take 8 turns. With a coarse 0.60 mm nylon, 4 turns are sufficient. When the knot is complete, pull strongly on the line to ensure that the knot is solid and does not slip.
Once completed, the knot takes the shape of a cylinder or barrel. The name half-barrel comes from the fact that the barrel knot is made up of two wires joined by two half-barrels.
1) Pass the line through the eye of the lure, hook or swivel, then make a loop with the end of the line "a".
2) Make 5 turns of line "a" on the main line, then enter line "a" in the start loop.
3) Moisten the knot before gradually tightening it by pulling on "b" while holding "a". Cut the free strand "a" protruding from the knot, between 3 and 5 mm from the knot.
