Confirm your depth micrometer is accurate. These gauges check if your micrometer starts measuring at zero. With six highly accurate reference depth points that range from 1″ to 6″, you can check the accuracy of your depth micrometer and adjust if it comes out of calibration over time. Twist the micrometer's spindle until the tip of the rod is touching the surface of the gauge block and check the reading. Once zeroed, your depth micrometer is ready to measure your parts.