Place your ruler against the item you want to measure.
Line up the "0" mark on the ruler with the starting point of the item you are measuring. The "0" mark will not have a printed "0" on the ruler but will be the first mark on the ruler prior to the "1" mark.
Locate the line on the metric side of the ruler that matches with the end point of the item you want to measure. For example, if the line matching the end is equal to the number "10," it means you have measured something 10 centimeters in length. If your item is 100 centimeters long, it is also one meter long, or 3.28 feet long.