This series of five introductory modules comes from Agilent Technologies' massive Educator's Corner Web site. It is mainly intended to teach high school students about some of the most fundamental principles of engineering, using a guitar to demonstrate concepts like frequency and tensile strength. At the same time, the material stresses the importance of critical thinking and taking an analytical approach to problems -- characteristics that are the sign of a good engineer. To encourage this mentality, the modules lead the user through a basic derivation of the formula for the frequency of vibration of a guitar string. This is initially done with very little hard math; rather, the derivation is primarily based on intuition, and it can be verified with mathematical analysis.