This 8-1/2 in. x 18-1/2 in. rectangle ruler by Creative Grids USA 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 in. 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 inch grids marked in 1/8 and 1/4 inch increments. Use the black numbers (printed on white dots) and the 1/4 inch grip sides to cut whole inches, while the white numbers (printed on black dots) and the 1/2 inch grip sides add the 1/2 inch seam allowance. Use the white 45 degree angle to trim half-square triangles in whole inch increments. Use the black 45 degree angle to trim half-square triangles in half inch increments. An additional black 45 degree line is placed so that two angles cross 1/4 inch 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 30 and 60 degree 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. The ruler slides easily over the fabric until pressure is applied. Then, the exclusive gripper holds the fabric in place while cutting, eliminating slipping and miss-cuts! This ruler comes with fully illustrated step by step instructions or scan the QR Code printed on the ruler to view a video demonstration.