Ensure parts are perfectly straight and square—these gauges detect surface deviations so small the human eye can’t see them. As you slide the lever on these gauges up and down, a dial test indicator moves along the vertical surface of your workpiece, measuring how straight and square it is. Checking for slight angles on machined parts or frames verifies they will align properly and function correctly. You can adjust the squareness of the gauges to fine-tune for differences in temperature and humidity and to maintain precision over years of use. Measure an object for height with the scale along the side of the gauge. The housing is cast iron, so the gauges are stable and stand up to frequent use.

Inspect micrometer spindle and anvil tips to identify whether they're worn or out of parallel. These discs help you keep your micrometer measuring accurately, especially after repeatedly measuring hard items such as ball bearings. Place them between the anvil and spindle and look at the resulting light pattern on the glass.

Optical parallels determine if your anvil and spindle are parallel. You’ll know your micrometer is out of parallel if the spindle side reflects a different number of lines than the anvil side. Each parallel includes four discs to check each quarter-turn of your spindle and identify where it has worn down.