Simple energy considerations, which have previously been employed to provide a rational basis for the principle of Saint‐Venant, are shown to lead to the conclusion that forces applied in the neighborhood of a rigidly fixed portion of an elastic solid can cause only local stress and strain. This principle indicates useful features of certain problems encountered in engineering, and is used here in the calculation of the stiffness of a thin layer of elastic material confined between rigid plates, under any kind of load applied to the plates.