If you fish you know that tying leaders to hooks or flys can seem to require three hands at times. I'm no different so I made this tool. After all fishing is all about the next fishing gadget; actually catching fish is a peripheral benefit. :-)
The top of the device is a small version of a machinist's clamp but made in brass so it won't rust in wet and salty environments. It's attached to a cylindrical aluminum (again, no rust) 'handle' which has a number of cutouts to hold leaders of various strengths. Each cutout has a small screw and washer to trap the free end of the leader so it won't unravel in the tackle box.
The interior of the 'handle' is bored out to form a small compartment for needles and other knot-tying aids. A threaded brass plug secures this compartment.
I'm normally sitting in a boat when I use this so I mount the hook/fly in the vise and clamp the 'handle' between my knees thus freeing both hands to attend to the knot tying. The brass plug could easily be adapted to a rod that fits into an oarlock or a magnet that holds the device to a steel tackle box or boat section.