Sweeping with Two Guides

In a sweep with two guides, every section plane that is normal to the origin trajectory has a profile section that is aligned to the vector defined by the O-X vector in that plane, scaled by the length of the O-X vector, and limited by the extents of the shortest trajectory. If there are two or more trajectories and the spline that connects them (as a profile) is tangent to the surfaces that contain the trajectory edges, then the spline not only scales and aligns to the O-X vector, but also deforms to keep that profile tangent, at all points along the trajectories, to the neighboring surfaces. The profile does not have to touch the trajectories, but the profile plane has to intersect with the trajectories.

You can also sweep with two closed trajectories.