if you decide to mark a regular plastic quilting ruler of the right size, and mark it, you could use come "invisigrip" or similar non-slip product on the side which will be on your fabric. The cuts you make with the Twister Tool don't leave much room for over cutting -- you'll be damaging the next row of blocks you need for your project. Think that's why the tool comes with the attached feet to keep it from slipping.