@@yo3429 yeah they are the regular 40x40 40x80 with a spacing of 40, now the problem was the BIG C extrusions are not :( thats why i wanted to drill these slots, and have some wiggle room to make the big ones parallel :) since i cant work so precise :) haha, now i can take up some slop. i try to make as much things possible to adjust. since i know i dont have machines or patience tom work 100% precise :) let alone draw haha