On a miter saw, when you're cutting a 90 degree cut, the miter saw reads zero. On a protractor, it reads 90. So it's an unending source of confusion for people. RON HAZELTON: So Mark, show me how it works.
A ruler is used to measure units of length, inches, feet and yards. Standard rulers have inches on one side and centimeters on the other. A typical ruler measures up to 12 inches, and is equivalent to 30.48 centimeters. This is also equivalent to 1 foot. Each inch on a ruler has markings in between that are a fraction of an inch.
How to Use a Metric Ruler. There are two types of scales commonly used on rulers; Fractional and Decimal. Fractional Rulers have graduations or marks based on fractions, for example 1/2, 1/4 1/8, 1/16, etc.. Decimal Rulers have graduations or marks which are based on the decimal system such as 0.1, 0.01, etc. Decimal Rulers can be based on any measuring system but are usually based on either the English measurement system of inches (in) or the Metric measurement system of millimeters (mm), centimeters (cm) and meters (m).