  Boxy edge-on profiles can be accounted for not only in models of barred
galaxies, but also in models of normal (non-barred) galaxies. Thus, the
presence of a bar is not a sine qua non condition for the appearance of this
feature, as often assumed. We show that a `boxy' or a `peanut' structure in the
central parts of a model is due to the presence of vertical resonances at which
stable families of periodic orbits bifurcate from the planar x1 family. The
orbits of these families reach in their projections on the equatorial plane a
maximum distance from the center, beyond which they increase their mean radii
by increasing only their deviations from the equatorial plane. The resulting
orbital profiles are `stair-type' and constitute the backbone for the observed
boxy structures in edge-on views of $N$-body models and, we believe, in edge-on
views of disc galaxies. Since the existence of vertical resonances is
independent of barred or spiral perturbations in the disc, `boxy' profiles may
appear also in almost axisymmetric cases.
