The Thimble Ruler Set by Lori Holt of Bee in my Bonnet includes 2 Thimble Rulers. They can be used to rotary cut or to trace templates to machine piece thimble shapes for your quilts! They were especially designed for convenience when using precut fabric squares in 5" and 10" sizes.
Photo credit goes to Lori Holt. Check out her blog, Bee in my Bonnet, for more pictures and ideas.