The Block Marker differs from other quilting squares as it measures from the center point out, which can be marked through the ruler. Made from a flexible and very durable acrylic. 12 different sized squares in one ruler. 17 inch to 12 inch square in the center and a 6 inch to 8.5 inch square with center point, in the upper right hand quadrant. The center point can be marked through the ruler. Slotted corners for accurate marking of the working area of a quilt block. Marked lines on The Block Marker are used to square up patchwork blocks before trimming. Can be used with a rotary cutter. Quarter inch seam allowance marked around the outside. Used in conjunction with the Sewing Revolution to ensure perfect place of embroidery or appliqué.