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The Castwell - Line to Leader Knot

By James Castwell

I learned this knot in 1945, I was ten then and with 'grass-mowing-money,' bought a used bamboo fly rod. It came with a reel, line, leader container and some flies. Over the years the flies have disappeared, the leader can is gone and a friend borrowed and broke the Granger fly rod into several pieces.

All I have left are fond memories and this knot. It was to tie the very fine end of a SILK fly line to a loop in a gut leader. Since a silk fly line is very small in diameter the resulting connection was hardly noticeable. It would not readily collect stream-born grass and would pass easily through the very small tip-tops and guides used on bamboo rods of that era.

So far, I have not been able to find an original name for it; so after half a century of looking and not finding one, I will put a name on it. The Castwell. I am positive it has another name, but it needs to be named now. In the many years of fly fishing I have shown it to a whole lot of people and none have ever seen it, or anything like it.

It is so devilishly simple it is actually hard to learn and remember. Be very careful to get it exactly right. In my lifetime of fly fishing it has NEVER FAILED. I have, over the years, used other knots for the 'line-to-leader,' connection. This remains my personal choice for all size leaders and fly lines. The tippet and leader have always failed and this knot has held. Will this work for the 'blue-water' big game stuff? I have no idea. That is a different ball-game.

The 'Castwell' uses a very small amount of fly line and can actually be backed off if needed. I cut it off to change a leader. If you change leaders often, you may use it to tie the short leader-loop butt section to your fly line. ~ J. Castwell

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Castwell's Line to Leader Knot

Addendum: 11/20/00 A reader sent us pictorial evidence this knot has gone by the name of 'LAP Knot,' originally having been used in Lapland. Specifically, this is a left hand version. The simplicity of this knot leads me to believe it must have been known by other names as well over the eons of human development. If you find yet more information on this, please contact me. JC

Addendum 2: Comes now this. A strong belief from a reader in Reykjavik, Iceland that this knot was known as a 'Flag Knot,' (fanahnutur) used by him as a youngster in the Boy Scouts when attaching a flag. More names? Keep them coming. JC

Addendum 3: From Frank A. Finley in St. Ignatius MT, "The 'Castwell' knot is also known as a weavers bend, and is used in looming rugs and cloth. It was designed to marry 2 different materials together (like silk and monofilament or gut). I never thought of using it for fishing, but have used it to thread rope and other cordage to lift deer from the ground when skinning. It really is a strong knot and small and simple as well." Thanks Frank! Any more? JC

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