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.
Get an English ruler. You will know it is an English ruler because it will have 12 lines that denote inches on the ruler. 12 inches equals 1 foot (0.3 m). The 1 foot (0.3 m) is broken down into inches. Each inch is broken down into 15 smaller marks, equaling 16 marks in total for each inch on the ruler.