Nail knot

The nail knot, also known as the tube knot or gryp knot, is mostly used in carp and fly-fishing. The nail knot was named because a nail was inserted as a guide when threading the line. Today, it is easier to use a small straw. The nail knot is an important fishing knot used to join two lines of different diameters and allows for line diameters to diminish down to the fly. I.E., it is useful for attaching your backing to the fly line, and your fly line to the leader, or tippet. The knot can be tied in multiple ways and is uniform.