The directions in which diamond polishes most easily. In practice, this direction is usually found by trial and error, although it is always away from an octahedron face and toward a possible rhombic-octahedron face. Facets parallel to the surface of a dodecahedron are the most difficult. The ease and rapidity of polishing also varies in different directions; i.e. from right to left the rate may be more rapid than from left to right.