Vernier depth gauges and combo depth and angle gauges are instruments used to find the depth of a hole and to determine angles. Vernier gauges have a graduated blade that’s lowered into holes until it makes contact with the bottom. The measurement is then taken on the vernier scale. Combo depth and angle gauges have a graduated rule attached to a base etched with markings at 30°, 45°, and 60°. They also have a locking mechanism in the base that allows the rule to be rotated so angles can also be measured.