This shell is related to solid state physics and structural chemistry. The program [http://www.cryst.ehu.es/cryst/pseudosymmetry.html PSEUDO] performs an evaluation of the pseudosymmetry of a given structure with respect to supergroups of its space group. [http://www.cryst.ehu.es/cryst/amplimodes.html AMPLIMODES] performs the symmetry-mode analysis of any distorted structure of displacive type. The analysis consists in decomposing the symmetry-breaking distortion present in the distorted structure into contributions from different symmetry-adapted modes. Given the high and low symmetry structures, the program calculates the amplitudes and polarization vectors of the distortion modes of different symmetry frozen in the structure. The program [http://www.cryst.ehu.es/rep/sam.html SAM] calculates symmetry-adapted modes for the centre of the Brillouin zone and classifies them according to their infrared and Raman activity. [http://www.cryst.ehu.es/rep/neutron.html NEUTRON] computes the phonon extinction rules in inelastic neutron scattering. Its results are also relevant for diffuse-scattering experiments.