a faceted curved surface created by adjoining flat faces between two curved lines, created by subdividing each line into an equal number of short segments and connecting between them

a surface created by generator lines that are perpendicular to the direction of creation of the surface

a surface that is flat in some direction at every point on the surface

saddle point set, convex skeleton, 1- star of a vertex surfaces closed compact connected non-orientable orientable polyhedral ruled smooth

(n) A surface produced by the movement of a straight-line generatrix controlled by a directrix to form a plane, a single-curved surface, or a warped surface.

In geometry, a surface S is ruled if through every point of S there is a straight line that lies on S. The most familiar examples are the plane and the curved surface of a cylinder or cone. The last two are special cases of ruled quadrics (which also include the hyperbolic paraboloid, the hyperboloid of one sheet, and the conical surface with elliptical directrix).