Remember when you had an offset gauge, ruler and adjustable square all in 1-tool. The WEN Aluminum Marking Gauge provides a variety of helpful woodworking applications for users of all kinds. Unlock the center knob to freely slide the gauge back and forth. This allows you to manually take caliper-grade measurements with 0.002 in. precision. Vernier scale includes both metric and imperial markings, depending on the needs of the task at hand.