Excuse the crudeness of this picture, I am trying to highlite the "webs" you will take your measurements from to assemble the rack correctly. Measure .300"from the outside edge of the bottom web and scribe a line. Then measure .54" from the outside of the short vertical web and scribe a line, do this to each side of the short vertical web. Assuming your short vertical web is .08" thick, you should have a 1" space between the points where the scribed lines meet. Drill your holes there. I hope I explained that correctly!