ClipArt ETC
"An oblique cone connecting two parallel pipes of different diameters... the true size of the base is not given in the top view and must be revolved until parallel to H."—French, 1911

Oblique Cone by Triangulation Connecting to Two Parallel Pipes of Different Diameters

"An oblique cone connecting two parallel pipes of different diameters... the true size of the base is…