Blood Knot: How to Join Two Fishing Lines
The blood knot (barrel knot) joins two lines of similar diameter with a slim, neat join that runs through rod rings. The classic for fly leaders and tippet.
The blood knot (or barrel knot) joins two pieces of line end to end. It makes a slim, symmetrical join that slides through rod guides, which is why fly anglers use it to build tapered leaders and add tippet. It works best when the two lines are of similar diameter and of the same material.
When to use it
Building or repairing fly leaders and adding tippet.
Joining two lengths of monofilament or fluorocarbon of close diameter.
Repairing a line that has been cut or damaged.
For lines of very different diameter, or braid to mono, use the double uni knot instead.
How to tie a blood knot
Overlap the lines. Lay the two ends side by side, overlapping by about 15 cm (6 in).
First wraps. Wrap the first tag end around the other line 5–6 times, then bring it back and pass it between the two lines at the centre.
Second wraps. Wrap the second tag end around the first line 5–6 times in the opposite direction, and pass it through the same centre gap from the other side — the two tags now point opposite ways.
Hold the centre. Keep the centre gap open with your fingertip so neither tag slips out.
Wet and seat. Moisten the knot and pull both standing lines apart slowly so the coils draw together into a neat barrel. Trim both tags close.
Tips
Use 5 turns on each side for line over about 10 lb, 6–7 turns for fine tippet.
If the two lines differ by more than about 20% in diameter, double the thinner line before wrapping, or switch to a double uni.
A finished blood knot looks like a tidy barrel with the tags exiting in the middle. Lumpy coils mean a weak knot — retie it.
Blood knot vs double uni
The blood knot is slimmer and neater. The double uni is easier to tie, handles different diameters and works with braid. Most lure anglers use the double uni; fly anglers keep the blood knot.
See all guides on the fishing knots page.
