For automotive and machining applications, a tool called a dial caliper is frequently used as a reliable precision tool that is relatively easy to operate. It is capable of measuring parts to the thousandth. And though it is, as just stated, more or less easy to use, it is important that a dial caliper be used correctly and read accurately.
Keeping in mind that it is far easier to show someone how to use a dial caliper than it is to simply write it on a piece of paper and read it, not to mention far more beneficial for both parties, here is a guide on how to use a dial caliper.