One guide curve and several section curves, vertical mode:

In the VERTICAL method, the sweeping coordinate system is defined as follow:

This method is useful to create evolutionary drafts, since if each section curve is a line in the XY plane of the sweeping coordinate system corresponding to each hooking point, with an angle with Y, then the mixed section curve will be a line with an evolutionary angle with Y axis of the sweeping coordinate system and will keep this angle compared with the vertical during the sweeping.