Sorry Tagger...its easy. Drill the eye hole, it was 1/2 inch on the jointed swimmer. Eye socket must be deep enough so the router bit I use to shape the edges can have enough room to cut. Then in the drill press put a router bit, I used a 3/4 inch, plug still has square ends, and very slowly drop it into the eye socket and let it carve the eye socket just the way you want it. (I stress very slowly as if you go too fast the router bit will chew and spin the plug at your head)
The smaller plugs are easier as I just use a round dremel bit to do this. A little sanding and they look great!
I hope this helps.
