The unification of the mechanical planar chiral stereogenic units of rotaxanes and catenanes, as we have recently demonstrated in the context of an analogous mechanical axial stereogenic unit , will facilitate future work in the field by highlighting that similar synthetic concepts are likely to be of use for both rotaxanes and catenanes. Furthermore, as the pantheon of mechanical stereogenic units expands, alongside recent developments in covalent stereochemistry , and applications of stereochemistry in molecular machines , it is essential that the field remains on a firm theoretical footing. Finally, our results suggest that the focus should shift away from the topological properties of the catenanes; although chemical topology is an intriguing topic, we are not aware of any property of catenanes that has been unambiguously linked to their topologically non-trivial nature. Alternatively, perhaps by separating their stereochemistry into topological and Euclidean varieties, as we have done here, it will now be possible to demonstrate a unique property of the former.