This is something I made to clamp onto the edge of a piece of wood, in this case it was cheap oriented strand I found rotting away in my garage, to make it able to finger joint into another piece. With the goal of turning garbage wood into a box for carburetor parts. This is made for a .625 or 5/8 inch flush cut router bit.
It worked well enough, not perfect though as the length/depth of the fingers and such could be optimized.
There are two pieces in this "thing" one of them is made to index off of the edge and the other is made to index off of an previously cut finger gap.