This is a very handy idea I got from the internet, there are some different versions, and I have adapted them slightly to my own specifications. The idea is to get a quick calculation of the amount of linen to use for a pattern based on the thread count of the linen and the number of stitches. I have used these rulers constantly and wouldn't be without them.
I cut enough linen from each thread count to equal size, stitched the ruler markings 2 over 2, and embellished with a simple design and the description of the linen count. Enjoy!!