20 1/2-inch x 20 1/2-inch Non-Slip Ruler. This 20 1/2-inch square features easy-to-read black and white markings printed in 1-inch grids marked in 1/8-inch and 1/4-inch increments. The exclusive embedded gripper dots hold the fabric while cutting when pressure is applied. The patented Turn-A-Round feature - which adds the 1/2-inch seam allowance - is incorporated into each ruler. Turn the ruler around to cut whole inches. A 90 degree angle is printed in black. White horizontal and vertical lines are printed on the square so the center of the ruler is easily distinguishable. Dashed lines are printed 1/4-inch away from two adjoining edges to aid in trimming seam allowances. Creative Grids rulers are made in the USA and are known for their exceptional quality, smooth edges, uncomplicated design. Most of all, they are known for their wonderful non-slip grip. They are easy to use, and cutting is a breeze thanks to the non-slip circles and strips on the back. Press down lightly on the ruler, and the non-slip circles grip the fabric. Yet, when you are not pressing down the ruler, it will slide easily over the fabric. The fine lines in black and white and the white circled markings allow for great accuracy and easy viewing on both light and dark fabric.