The blood knot, sometimes called a barrel knot, is used to join two sections of monofilament or fluorocarbon of similar diameter, such as when adding a topshot of new line onto a half-filled reel spool. Use it to add a shock leader to the end of the mono main line, such as when adding a length of 30-pound leader to 15-pound main line. When the two mono lines are of greatly dissimilar diameters (eight-pound-test to 30-pound shock leader), it’s a good idea to double the lighter line. The knot is then called the improved blood knot. Fly fishermen use the blood knot to build tapered leaders starting with 30- or 40-pound-test and reduce the leader taper in several segments down to a less visible tippet of 12- or six-pound-test or lighter.
NOTE: For illustration purposes, 80-pound-test Hi-Vis TUF-Line Dacron was used for the photos taken by Linda Barrett.