Calibration typically checks the error at 3 to 5 points along the range. Only one can be adjusted to zero. If the micrometer is in good condition, then they are all "so near to zero" that the instrument seems to read essentially "-on" all along its range; no noticeable error is seen at any locale. In contrast, on a worn-out micrometer (or one that was poorly made to begin with), one can "chase the error up and down the range", that is, "move" it up or down to any of various locales along the range, by adjusting the sleeve, but one cannot "eliminate" it from all locales at once.