Although the five-fold world is aperiodic, its constituent polyhedra are still amenable to modularization. Various schemes exist, among which one of the most ingenious is Koski's. Koski's mods derive from the golden cuboid, a brick with edges phi, 1 and 1/phi. These 3 edges plus distinct face and body diagonals give a set of 7 lengths, any six of which may be used in a tetrahedron. Given these base measuring cups, Koski allows each to grow or shrink by powers of phi, and finds the five-fold shapes have both algebraic and geometric equivalence to sums of such modules.