The study of nanoscale tribology is an active and rapidly developing area of research which poses fundamental scientific questions whose study and understanding carry great technological potential in the field of friction, wear, and lubrication. When considering nanoscale materials junctions surface commensurability often plays a crucial rule in dictating the tribological properties of the interface. The present review surveys recent theoretical work aiming to provide a quantitative measure of the crystal lattice commensurability at rigid materials interfaces and relating it to the tribological properties of the junction. By considering a variety of hexagonal layered materials including graphene, hexagonal boron nitride, and molybdenum disulfide it is shown how a simple geometrical parameter, named the registry index, can capture the interlayer sliding energy landscape calculated via advanced electronic structure methods. The predictive power of the methodology is further demonstrated by showing how the registry index is able to fully reproduce experimentally measured frictional behavior of a graphene nanoflake sliding on-top of a graphite surface. It is shown that generalizations towards heterogeneous junctions and non-planar structures (e.g. nanotubes) provide a route for designing nanoscale systems that present unique tribological properties such as robust superlubricity. Future extensions of the method towards nonparallel interfaces, bulk materials junctions, molecular surface diffusion barriers, and dynamic simulations are discussed.