This ruler combines the practicality of a ruler and magnifying lens, and the simple physics of harnessed natural light. Lay the ruler directly on top of your materials to double the image size; the optical quality lens is specially shaped to gather and direct ambient light to the viewing area. The inch and metric scales are set above and below the magnified viewing zone. Smooth notches at the ruler's end create a comfortable grip and a thin red place-holding line helps with tasks as varied as numbers crunching, checking blueprints, marking sewing patterns, leisure reading, and more. slide ruler