For several years I used the permanent leader butt with Perfection loop as described above and used loop to loop connection with my leader. A few years ago I switched to using furled leaders. Most of my fly lines come with a welded loop, and for a while, on those that didn't come with a loop, I would whip finish or nail knot a loop on the end of the line. One day a friend wanted to try out a new rod. The line on the reel was also new, with no leader in place. As we were rather spoiled by use of the Tie Fast knot tool, none of us could easily apply a nail knot to the loopless fly line. I then remembered the Castwell knot that I learned on this forum many years ago. I had to look it up on my phone to be sure I remembered it correctly. When I showed my friends they were very skeptical. I have had some very experienced flyfishermen tell me that knot can't hold, but they are wrong. It will hold firmly to a thread furled leader, a monofilament furled leader, or just to a loop on a monofilament leader. Over the past two years I have been using the Castwell or lap knot whenever my fly line comes without a loop, and so far it has never failed me. It is far smaller than a nail knot and passes through guides and tiptops easily.

Larry