Editing Micrometer (device) (section)

===Zeroing===
On most micrometers, a small [[wrench#spanner wrench|pin spanner]] is used to turn the sleeve relative to the barrel, so that its zero line is repositioned relative to the markings on the thimble. There is usually a small hole in the sleeve to accept the spanner's pin. This calibration procedure will cancel a zero error: the problem that the micrometer reads nonzero when its jaws are closed.