Belfry, pretty much exactly what I did. Wasn't going to spend all those $$$ for a ruler I may never use again. (But I do love this pattern and will more than likely do it again.) Or try this: Make a paper template. Mark an 8 inch square in the middle of a large sheet of paper. Measure 4-1/2'out from each side. this will be a 16-1/2'' square. Double check by cutting the 8'' portion out, and center the star in this hole in the template. This will give you the outer edges of your block. This, too, is probably as clear as Belfry's mud.