A micrometer allows a measurement of the size of a body. It is one of the most accurate mechanical devices in common use. This document introduces this instrument.
If you are a student in the Physics laboratory at the University of Toronto, the material discussed here is also covered in the Commonly Used Instruments section of the First Year Laboratory Manual. There is also a videotape on using a Micrometer and a Vernier Caliper available from the laboratory technologists.