The Nail Knot, also known as the Tube Knot or Gryp Knot, is commonly used in carp and fly fishing to securely attach a line to a leader without adding bulk. It's ideal for joining two lines of different diameters, allowing the line to taper smoothly down to the fly. The knot is tied by wrapping the working end around the standing part and a small tube or nail (hence the name), which is then removed before tightening the knot.
