The Blood Knot
The Blood Knot is probably the single most important knot in an angler’s armory and can be used to effectively join two lengths of line of similar breaking strain or diameter together. Make sure that you use at least 5 turns on each side to ensure that the knot works effectively.
Take your two line ends and line them up parallel to one another with a 6 inch overlap.
Wind one line at least five times around the body of the other and pass the end back under itself.
Repeat with the other side, then pass the end through the central loop in the opposite direction to the first end.
Moisten and draw the knot tight by pulling on the main lines, not the free ends. Trim neatly.