This 16.5″ square ruler includes centered horizontal, vertical and diagonal lines. The 1/4″ seam allowance is marked on the entire outside edge of the ruler. Centre the ruler over any appliqued or embroidered block and trim – it’s that easy. To square up a pieced block, place the correct size of the ruler over the block to be trimmed. to trim a four-patch, for instance, place the horizontal and vertical lines of the ruler on the seam lines of the four-patch. Trim the outside edge of the block. Fussy Cutting – to showcase a particular design in the fabric this is called fussy cutting. This technique adds drama and eye appeal to any project and these rulers make the process quick and easy. To fussy cut, centre a design in the solid squares – printed in 1″ increments. The drilled holes at the 1/2″ markings between the squares let you mark and add the seam allowance to your fussy cut piece. Use a water soluble pen to mark through the drilled holes and then trim.