At a glance
What this knot is for
- Joins
- Two lines of similar diameter
- Line types
- Monofilament and fluorocarbon of similar diameter. Not suited to braid or to joining lines of very different thickness.
Reach for it when
- Joining two lengths of mono or fluorocarbon of close diameter
- Building tapered leaders, particularly for fly fishing
Method
How to tie the blood knot
- 1Overlap the two line ends by 15–20cm.
- 2Wrap one tag end around the other standing line 5 times, then bring it back and pass it between the two lines at the centre point.
- 3Wrap the other tag end around the first standing line 5 times in the opposite direction, then pass it back through the same central gap, from the opposite side, so the two tag ends cross in the middle.
- 4Moisten the knot, then pull the two standing lines apart steadily so the wraps on each side close down and the two tag ends are trapped in the centre.
- 5Trim both tag ends close to the knot.
Work on a flat surface with enough line in your hand to pull the knot down firmly, and check the wraps sit neatly before you trim anything away.
Why it works
- Neat and streamlined for its strength when the two diameters are close
- Long-standing standard for fly leader construction
Where it lets you down
- Reliability drops sharply once diameters differ by more than a size or two — use a surgeon's knot instead
- Fiddly with stiff fluorocarbon or in cold conditions
- Not a braid knot
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The tackle this knot ties
The knot itself costs nothing — it joins your line to the tackle you buy. This search shows the general category this knot is tied onto, never a named brand or model.
Shop fly fishing tippetAlternatives
Knots that do a similar job
Used in
Fishing methods that use this knot
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Check the rules where you fish
Some waters restrict tackle or methods — barbless hooks, lead sinkers, certain rigs and line types. Confirm the rules of the water you are fishing before you use any rig or knot.