What the Duncan Loop Does
The Duncan loop is a knot that ties your line to a hook or lure while leaving a small loop between the knot and the eye of the hook. That loop lets the hook move freely side to side, which gives artificial lures more natural action in the water. The knot holds well under load and is quick to tie once you know the motion.
Anglers use it most often with crankbaits and other lures where movement matters, but it works just as well with live bait rigs. The loop can slip if you tie it wrong or use line that's too thin for the knot's grip, so the technique matters.
Key Takeaways
- The Duncan loop creates a small loop at the hook eye that lets lures move more freely than a tight knot would allow.
- You tie it by wrapping the line around the hook shank, threading back through the first loop, then cinching the knot while leaving the final loop open.
- The knot works best with line in the 8-pound to 20-pound range; very light line may slip under pressure.
- Test the loop by hand before casting — it should move freely but not so loosely that the knot slides on the hook shank.
Step-by-Step Tying Instructions
Start with about 6 inches of line extending past the hook eye. Hold the hook in your left hand (if you're right-handed) with the eye pointing away from you. Take the tag end of the line and wrap it around the hook shank, making a loop that crosses over itself.
Thread the tag end back through that loop from underneath, so the line forms a figure-eight shape. Now thread the tag end through the loop again — this time going through the same loop a second time. Pull the tag end tight while holding the main line steady. As you tighten, the knot will cinch down on the hook shank, but leave the small loop at the eye open. Trim the tag end close to the knot.
The loop should be loose enough to move when you wiggle it with your finger, but tight enough that it doesn't slide along the hook shank when you pull the main line. If the loop moves too freely, the knot wasn't cinched enough. If it doesn't move at all, you've tied it too tight and lost the benefit of the loop.
When to Use the Duncan Loop Instead of Other Knots
Choose the Duncan loop when you're fishing lures that need to move independently of the line — crankbaits, soft plastics on a jig head, and topwater plugs all benefit from the extra freedom. The loop reduces line twist and lets the lure respond to rod movement more directly.
If you're fishing a tight-line technique where you want the hook to move exactly as you direct it, a regular clinch knot or improved clinch knot will serve you better. For live bait where the bait's own movement is doing the work, either knot works, though many anglers stick with the improved clinch for simplicity.
In saltwater, the Duncan loop is less common than in freshwater, partly because heavier line and larger lures make the loop less noticeable and partly because tradition favors other knots. But it still holds in saltwater if you use line heavy enough for the knot to grip.
Common Mistakes That Weaken the Knot
The most frequent error is not threading the line through the loop twice. Some anglers thread it once and cinch, which creates a knot that looks right but won't hold under sudden pressure. The double pass is what gives the Duncan loop its grip.
Another mistake is cinching the knot too tight before you've positioned the loop. Once you pull hard, you can't adjust the loop size without starting over. Set the loop size you want, then tighten gradually while checking that the loop stays where you intended.
Using line that's too light for the hook size is also common. A 4-pound line on a size 2/0 hook may slip under the weight of a heavy lure or a strong fish. Match your line weight to your hook and lure — the knot needs enough line surface area to grip.
Testing Your Duncan Loop Before You Fish
After you tie the knot, hold the hook in one hand and pull the main line with the other. The knot should not slip on the hook shank. If it does, untie and retie — the knot wasn't cinched enough or the line is too light.
Wiggle the loop with your finger. It should move freely but not rotate all the way around the hook eye. If the loop is frozen in place, you've tied it too tight and should retie with a slightly larger loop in mind.
Cast a few times in the air before you fish. Watch how the lure moves. If the lure feels sluggish or doesn't respond to your rod movement the way you expect, the loop may be too tight. Retie with a slightly larger loop and test again.
Variations and When They Matter
Some anglers tie a non-slip loop knot instead, which is similar but uses a different threading pattern and creates a more permanent loop. The non-slip loop is stronger but less adjustable — once tied, you can't change the loop size without starting over.
The Palomar knot is another alternative that's faster to tie and holds very well, but it doesn't create a loop at all — the line goes straight to the hook eye. Use the Palomar when you want maximum strength and don't need the lure to move freely.
For very small hooks or ultralight line, some anglers prefer the improved clinch knot, which is simpler and less likely to slip on tiny hooks. The trade-off is that you lose the free-moving loop.
Frequently Asked Questions
Can I use the Duncan loop with braided line?
Yes, but braided line is slippery and the knot may slip more easily than it would with monofilament. Tie it the same way, but cinch it very tight and test it hard before fishing. Some anglers add an extra wrap around the hook shank with braided line to increase grip.
How big should the loop be?
The loop should be about the width of a pencil — roughly a quarter inch. Large enough that the lure can move freely, small enough that the knot stays tight on the hook shank. Adjust based on how the lure feels when you cast and retrieve.
Will the Duncan loop slip if I set the hook hard?
A properly tied Duncan loop will not slip under normal fishing pressure. If it does slip, the knot wasn't cinched enough or your line is too light for the hook size. Retie and test again before fishing.
Is the Duncan loop stronger than a clinch knot?
They're roughly equal in strength when both are tied correctly. The Duncan loop's advantage is lure movement, not strength. If you need maximum strength and don't care about lure action, use an improved clinch knot instead.
Can I tie a Duncan loop with one hand?
Not easily. The knot requires holding the hook steady while threading the line twice through the loop. Use both hands, especially when you're learning. Once you've tied it many times, you may develop a faster technique, but the basic motion needs two hands.