I recently began tying articulated leech patterns for salmon fishing in Alaska. I have been using two hooks to make the fly and cutting off the curved section of the lead hook after the fly is complete. This is not only expensive - each fly takes two high quality hooks - but care must be taken in cutting the hook so as not to leave a sharp end that can cut the connection between the two parts of the fly, when the fish fights the hook.
These articulated fly shanks take the place of the lead hook. Each one is less expensive than the hook it replaces and avoids the problem of leaving a sharp wire after making the cut. They are high quality material and the different lengths give me the option of varying the size of the flies I am tying.