Originally Posted by
cjsews
Make sure you trim on all sides. Have the halfway measurements in the very center. If you are trimming to 7 1/2 unfinished, you will have to put the 3 3/4 inch line through the center block. Or if you are trimming to 8 inch unfinished the lines of the ruler should be the 4in mark thru the center of your block both ways.
This is a much more concise description than I would have written. It's exactly what I would do. You can master this..be patient with yourself.