I saw an Eleanor Burns video and in that she stated that all you really need is a 6X24" ruler but that a big square is handy such as the 12-1/2" square ruler. She has a really big square for squaring up corners but she said that it is one of those "extras" that would be nice. Next ruler I get will be that big one!! LOL I have an abundance of rulers and will be glad when my sewing room is done so that I can have everything in its place!! I spend a lot of time looking for whatever!! Especially the fabrics I have unless they are in a box with the pattern to make it easy to go and sew the pattern. Thanks for posting. Piece and blessings, Vicki