  In this paper we address the problem of interpolating a spline developable
patch bounded by a given spline curve and the first and the last rulings of the
developable surface. In order to complete the boundary of the patch a second
spline curve is to be given. Up to now this interpolation problem could be
solved, but without the possibility of choosing both endpoints for the rulings.
We circumvent such difficulty here by resorting to degree elevation of the
developable surface. This is useful not only to solve this problem, but also
other problems dealing with triangular developable patches.
