The model shows two lines skew to each other, which intersect the z-axis of a Cartesian coordinate system orthogonally. On both lines congruent series of points are chosen and corresponding points are united by straight lines, the correspondance being such, that the z-axis belongs to that latter family of lines. This family of lines generates a hyperbolic paraboloid, the ruling plane of which runs parallel to the chosen skew lines. Rotating around the z-axis the family of the above mentioned uniting lines generates a family of one-sheet hyperboloids of revolution, a so-called osculating pencil.