Relation between the translation symmetry of the atomic pattern of rigid twist boundaries and their energy is analyzed. It is shown that the low energy of special twist boundaries cannot been explained by the coincidence model, since the energy contribution of the regions of good fit is exactly compensated by the contribution of the regions of bad fit. The geometrical condition that ensures the low energy of the boundaries with special misorientation angles is the coincident sites of the reciprocal two-dimensional lattices of crystal planes parallel to the boundary. in direct space, this condition means the existence of common Bravais translations for these planes. so that the low energy of special boundaries is related to the short-period structure of their patterns.