Check more than once to ensure the bolt cannot fit into a smaller hole.
Some thread gauges may look like a pocket knife. If you have one of those, open the thread gauge up by pulling out the first gauge.
If you are using a thread gauge that unfolds like a pocket knife, you’ll need to unfold each gauge and press it up against the threads instead.
Double-check the thread measurement by rubbing the bolt on the gauge a few times. It can be really tough to spot a half millimeter difference in bolt threads, so once you have your thread measurement, do the test one more time to make sure you got the same result. [7] X Research source
