Depth needs to be measured in many situations – sometimes by simply putting a precision rule into a hole or slot and determining a measurement by eye. Depth gages vary in form, complexity, cost and accuracy. The most accurate are depth micrometers (electronic, dial and vernier) and dial indicator depth gages. electronic depth gage variations are available, with or without coolant protection, and optional data output. They offer very good accuracy as do dial and vernier depth gages. Less complex and precise tools, rule gages and combination rule gages are also available. precise tools, rule gages and combination rule gages are also available.