This document provides an introduction to nondestructive testing (NDT) methods. It defines NDT as using noninvasive techniques to determine the integrity of a material or structure without causing harm. The six most common NDT methods are described briefly: visual inspection, liquid penetrant testing, magnetic particle testing, radiography, eddy current testing, and ultrasonic testing. NDT is used at various stages of production and in service to inspect for flaws and damage, monitor quality, and ensure safety and reliability.