Examples of vibro-impact mechanical and structural systems are not uncommon. Such systems are capable of exhibiting an interesting spectrum of non-smooth dynamic behavior when a characteristic changes abruptly. However, they present strong challenges to the analyst and designer trying to predict dynamic behavior. This paper considers an example of a rigid body (a rectangular block) that is placed on a flat surface that then oscillates in a seesawing, or tilting, motion. Given this kind of harmonic base excitation the free-standing block then responds accordingly, often by rocking. In this study the overturning characteristics of the block are of special interest. The motion is considered to take place in a vertical plane with no bouncing or sliding allowed. The outcome of experimental testing is compared with intensive numerical simulation. ©2010 Society for Experimental Mechanics Inc.