A diagram on the parts of a vernier calipers.
Step 1: Open the outside jaw.
Step 2: Close and lock the vernier caliper using the locking screw.
Step 3: Read the number of the main scale just before the zero line of the vernier scale.
Step 4: Read the number of the vernier caliper that alight with one of the line of main scale.
Step 5: multiply the line that alight with the main scale by the length of the smallest division on the vernier scale.
Step 6: Add the two numbers that were found in step 4 and 5 to get the final reading.