Several years ago, I attached a furled flouro leader ( shorb loop at the butt end ) to a Rio nymph line.

Over the years, that set up has accounted for "countless" trout and some whitefish. But the real tests have come intentionally breaking off up to 0X tippet and intentionally not breaking off several Clearwater B run steelhead.

Most recently, I hooked up and landed a 36" steelhead after a 20 plus minute tussle with this setup.

A couple days ago, a knot formed at the point where the thingamabobber was placed on the leader. I had to remove the leader by cutting the tip of the fly line before I could remove the thingamabbber and deal with the knot in the leader.

What became evident in that process was how little fly line is sacrificed when tying, removing, and retying the Castwell Knot. Maybe a half inch, total.

So besides how small and strong and durable and simple to tie this knot is, it is very efficient in terms of how little of the tip end of the fly line it takes.

You can find a tutorial for tying the Castwell Knot by going to "Features" on the Home Page menu and scrolling down to "Knots."