Blood Knot

The Blood Knot (also called the Barrel Knot) has been the standard line-to-line connection in fly fishing for well over a century. Its symmetrical design creates a clean, compact join between two lines of similar diameter, making it the go-to choice for building tapered leaders and attaching tippet sections. The knot sits inline with the leader, passes smoothly through rod guides, and holds reliably in monofilament and fluorocarbon — the two materials used most in leader construction.

How to Tie the Blood Knot

1. Overlap the two tag ends by about 6 to 8 inches, with the lines pointing in opposite directions.
2. Wrap the first tag end around the second standing line 5 times, then tuck the tag end back through the gap between the two lines at the center.
3. Wrap the second tag end around the first standing line 5 times in the opposite direction.
4. Tuck the second tag end through the same center gap as the first, but entering from the opposite side so the two tag ends point away from each other.
5. Moisten the knot thoroughly and slowly draw both standing lines apart to seat the wraps evenly.
6. Trim both tag ends close to the knot body.

When to Use This Knot

The Blood Knot excels whenever you need a slim, reliable join between two lines that are close in diameter. It is the backbone of custom fly fishing leaders.

• Building tapered leaders from sections of decreasing-diameter monofilament or fluorocarbon
• Attaching a new tippet section to an existing leader
• Joining two pieces of similar-weight monofilament for general freshwater rigging
• Repairing a broken leader streamside when a quick, clean splice is needed

Pro Tips

• Keep the diameters of the two lines within two sizes of each other; the knot weakens significantly with large diameter differences.
• Use 5 wraps on each side for standard monofilament, and add an extra wrap or two when using thinner tippet material below 4X.
• Hold the center gap open with a finger or your teeth while tucking the tag ends — losing the opening is the most common tying mistake.
• Test the finished knot by pulling firmly on both standing lines before trimming; a properly seated Blood Knot will feel solid with no slippage.

Pros and Cons

Pros:

• Very slim profile that glides through rod guides with minimal resistance
• Symmetrical design distributes stress evenly across both lines
• Time-tested reliability in monofilament and fluorocarbon
• Ideal for building custom tapered leaders with precise taper transitions

Cons:

• Difficult to tie with lines of very different diameters — strength drops sharply
• Not suitable for braided line, which slips out of the wraps
• Requires practice to consistently tuck both tag ends correctly through the center
• Can be challenging to tie in cold or wet conditions with numb fingers