Check step height, gap width, and the distance between narrow slots to make sure machine and engine parts seamlessly align. These highly precise gauges access spots where calipers and other measuring tools can’t fit. They’re often used to test the height of rivets and other fasteners to ensure loads are distributed evenly. Made of stainless steel, the gauge body and blade resist corrosion.

You’ll need to calibrate the gauge before each use for accurate readings. Press both jaws into the included zero-setting block to zero the gauge. Before measuring internal gaps and narrow slots, you’ll also need to set a baseline with a micrometer (not included). Line up the gauge’s jaws with the micrometer’s face.

These gauges have a power button, but you can also wake them up just by picking them up. Don’t worry about this draining the battery—the gauge turns off after five minutes of inactivity.