I know I have seen this, but it has slipped my mined(whats left that is). I am building to bookcases and have a few more lined up aftet that. I plane on makeing a jig to use the router. Plans are to use 1/4" ply and space the holes1.5" apart? and have it set for 1" back from the edge or 1-1/2" from the edge and 9" from the top and bottom. What size collar should I use for the router? If I am using 1/4" pins, would 3/8" or 7/16" work?