This 8-1/2" x 18-1/2" rectangle ruler is a workhorse. It is the perfect size to span the most popular size of rotary cutting mats. And, since it is 25% smaller than the original 24-1/2" version, it is easier to manipulate. The wide width makes it the perfect choice to square up corners and borders. It features easy-to-read black and white markings printed in 1" grids marked in 1/8" and 1/4" increments. Use the black numbers (printed on white dots) and the 1/4" grip sides to cut whole inches, while the white numbers (printed on black dots) and the 1/2" grip sides add the 1/2" seam allowance. The ruler slides easily over the fabric until pressure is applied. Then, our exclusive gripper holds the fabric in place while cutting, eliminating slipping and miss-cuts! Use the white 45º angle to trim half-square triangles in whole inch increments. Use the black 45º angle to trim half-square triangles in half inch increments. An additional black 45º line is placed so that two angles cross 1/4" away from the outside edge. Use these markings to square up flying geese units; squares set on point or mark cross-hatching. The ruler also features a 30º- 60º angle. White horizontal and vertical lines are printed on the rectangle so the center of the ruler is easily distinguishable. Use these lines to fussy cut stripes and borders. Creative Grids Rulers have a MAP (Minimum Advertised Pricing) Policy. Please do not advertise them for less than the suggested retail.