In 1961, Wasserman and Frisch recognized that interlocking two non-stereogenic rings can result in a chiral catenane where the enantiomers are related by inverting the relative orientations of the two rings. A decade later, Schill identified a similar phenomenon when a ring encircles an axle in a rotaxane, and that geometric isomerism is also possible. Since these first reports, the pantheon of mechanical stereogenic units in simple [2]catenanes and [2]rotaxanes has expanded beyond those envisaged by Wassermann and Gaeta and Neri recognized that catenanes can also express mechanical geometric isomerism and more recently, we identified a previously overlooked class of mechanically chiral rotaxanes, 5a and re-analyzed the planar chiral stereochemistry of catenanes to show that, although they were hitherto simply described as "topologically chiral", this is not an essential characteristic of this stereogenic unit. The recent discovery of new conditional 7 mechanical stereogenic units contrasts with covalent organic stereochemistry where, although new pathways of isomerization and previously overlooked expressions of atropisomerism have been reported, the archetypal stereogenic units (centers, axes, planes, helices and multiple bonds) 10 are long-established. This raises an obvious question; are there any mechanical stereogenic units of [2]catenanes and [2]rotaxanes still lying undetected? Here we provide a simple stereochemical analysis that shows the answer is yes; working from first principles we identify a previously overlooked rotaxane geometric stereogenic unit, but also demonstrate that this is the final one to be found -our pantheon is complete (Figure ). Using concepts developed for the synthesis of mechanically planar chiral molecules we demonstrate the first stereoselective synthesis of these new type 2 mechanical geometric isomers.