  We provide algorithms to reconstruct rational ruled surfaces in
three-dimensional projective space from the `apparent contour' of a single
projection to the projective plane. We deal with the case of tangent
developables and of general projections to $\mathbb{p}^3$ of rational normal
scrolls. In the first case, we use the fact that every such surface is the
projection of the tangent developable of a rational normal curve, while in the
second we start by reconstructing the rational normal scroll. In both instances
we then reconstruct the correct projection to $\mathbb{p}^3$ of these surfaces
by exploiting the information contained in the singularities of the apparent
contour.
