Doing this out of a request. This comes off the fly tying tutorial section of Steelheader.net. Here is a step by step instruction of tying the string leech. (this tutorial is property of and is being used w/permission from Steelheader.net).
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I tie up something similar, but it's a double hook setup. This is a request from a friend to tie. But, there is a true string leech that I've heard of but never tried. Heard it works really good. May have to try one now that I have one tied up. Found the pattern, and it's fairly simple pattern. But can be a bear to tie. Took some examples on how to tie and made up my own "mock" vise to tie it. It is odd to tie, and hard to make a nice head on it.
First, you want to take a smaller hook. Not your standard fly hook, I'm using an octopus hook in black. You don't have to do an eggloop on the hook. Simply tie in with either an improved cinch, I use a knot (have no idea of the name) but is extremely strong and meant for superlines. I used some 30# backing for the leech line. But you can use mono, or whatever. But the pattern calls for dacron type line. Make the leech however long you want, and finish the loop at end with a double surgeons knot. Here's what it should look like.
Not comes the fun part. Making a vise. They gave an odd instruction, but I retrofited one. You have to have the line tight so you can successfully tie down the materials. I simply hooked the hook onto my C clamp vise. Then, put a rubberband into the open loop created by the DBL surgeons knot and placed the rubberband over my tubefly vise (with the tube attachent taken off). The heavy pedestal base of the tubefly vise held whole thing in place nicely. Looks like this.
You don't have to be exact, but tie in the beginning of the thread. This isn't always easy. But I started the thread inside the loop and did a couple turns of thread. Sealed in the thread. I did a few more turns to make sure I had a good base. If you don't put a few wraps down, it'll come loose when you add materials.
Tie in the flashabou. I'm using just silver, but any color can be used. Just need a few fibers, not alot. Make sure you give them a few wraps, and make sure they are long enough to touch the hook.
Pick out a rabbit zonker strip. I'm using pink, but any color can be used. Make sure it's same length as flashabou and hook. Tie in just above the flashabou.
Do a few more wraps and you're done. Hard to whip finish this badboy (too much in your way). I simply pulled out of the makeshift vise and did the best whipfinish I could. But with a floppy base, hard to do. But when all is done, this is what it looks like.
Simple to tie, and heard they're very effective. Something for you to try out this coming steelhead/salmon season.