Video

Anglers use this (Half Blood) knot to attach a line to a hook, ure or swivel. Pull on the standing part of the line to convert the twists into snug wrapping turns. The Clinch Knot is an easy variant of the Half Blood Knot that may be more secure.

Reference:
Budworth, G. (2002). The Ultimate Encyclopedia of Knots & Ropework. Barnes & Noble