The seismic performance of ancient masonry structures is largely governed by out-of-plane failure mechanisms. When the masonry quality ensures a monolithic behavior, the dynamic response of a rigid rocking block, modeled according to Housner's approach, can effectively capture the out-of-plane capacity. However, conventional analyses often neglect the influence of the vertical component of seismic action, which can significantly affect the response of the rocking element and, consequently, its seismic vulnerability. This study investigates this aspect by analyzing a set of natural earthquakes that occurred in Italy over the past twenty years, considering both the vertical and the horizontal components. Furthermore, both one-sided and two-sided rocking motions are considered to account for the different boundary conditions typical of existing masonry walls.