CS has a patent on her ruler but the block it makes is an old block and has been around many years. Anita Grossman has a book showing how to mark your 6" ruler to make this block, it came way before Marsha did the twister ruler. I made this block many years ago as a tessalation for my guild. There is only one piece that you cut out 4 times to get the pinwheel. Uses a lot less fabric than the ruler method.