Tube Fly Adapter Needle
The flat brass fin is gripped in the vice.
Slackening the knurled wheel allows the pin to be withdrawn.
The fly tube is fitted over the pin which is refitted into the adapter
The pin is pushed in as far as to jam the tube between the adapter and the stud on the head of the pin, before the knurled wheel is tightened up to lock the tube ready for tying.