Bucking bars are used with pneumatic percussive rivet tools for airplanes, ships, and heavy vehicle constructions. The rivet is actually flattened by the bucking bar instead of the riveting hammer when the force is transmitted to the contact point between the rivet stem and the bucking bar. It has been proven that the operator who is holding the backing bar receives higher level of vibration than the person who is operating the rivet hammer. However, more attention has been given to the design modifications of the rivet hammer than the bucking bars which may due to the economic reasons. (The price of hammer is 50 to 100 times higher than the bucking bars’ price.) In this paper, the vibration characteristics of the bucking bars, the applications of vibration isolation and damping to the bucking bars, the optimum mass distribution calculated by a two degree-of-freedom model and the comparative results of the conventional bucking bar and ergonomically modified bucking bars are presented.