First punch out a scallop with the Stampin' Up! Use Dotto repositionable adhesive on one side of the punched out scallop to adhere it to a piece of copy paper. You must use copy paper as another sheet.
For anyone who likes creating things with paper, this is one of the best measurement shortcuts. Learned in a bookbinding workshop led by Cherryl Moote. If you need to divide a rectangular sheet of paper into equal pieces.