A vehicle sill reinforcement includes a first elongate member and a second elongate member. Each of the first elongate member and the second elongate member includes steps and walls disposed in alternating arrangement along an axis. The walls of the first elongate member are fixed to the walls of the second elongate member. The steps of the first elongate member and the steps of the second elongate member are aligned along the axis and define cavities therebetween. The steps and walls of the sill reinforcement resist buckling in response to both vertical and horizontal components of impact force applied to the sill reinforcement.