  We present a simple resonant Hamiltonian model for the vertical response of a
stellar disk to the growth of a bar perturbation. As a bar perturbation grows
stars become trapped in vertical Inner Lindblad resonances and are lifted into
higher amplitude orbits. The vertical structure of a boxy and peanut shaped
bulge as a function of radius and azimuthal angle in the galaxy plane can be
predicted from the strength and speed of the bar perturbation and the
derivatives of the gravitational potential. This model predicts that stars on
the outer side of the resonance are lifted higher than stars on the inner side,
offering an explanation for the sharp outer edge of the boxy/peanut.
