A micrometer is a small tool that is used for measuring short distances accurately. It is a type of caliper that can measure the depth, length and thickness of any object that will fit into it. A micrometer screw gauge uses a spindle that is moved by turning a small screw. It is precisely machined and can measure the thickness of a piece or the length of the head of a nail. It can generally measure objects down to hundredths of a millimeter.
Place the object you wish to measure between the jaws of the micrometer screw gauge.
Turn the ratchet knob on the end of the micrometer to close the jaws until the object is secured.
Turn the ratchet for three more clicks after the object is secured. Lock the gauge by flipping the thumb switch.
Take the measurement of your object. There is a scale measured in millimeters to the left of the revolving thimble. That will be your first reading. The thimble itself measures the hundredths of a millimeter and is lined up with the main scale.
Tighten the ratchet to the manufacturer's instructions, but never over-tighten because it could damage the machine and result in inaccurate measurements.