Create the illusion of curves with this Curvy Log Cabin Trim Tool. Sew four blocks together to piece a circle. Mark the wrong side of the center square through the holes on the ruler to ensure a perfect seam allowance. Then sew a round two narrow and two wide and trim. Add two more rounds to complete a perfect 8 inch finished block. The cutting requirements for the center square and the narrow and wide strips are printed right on the ruler.