Finite dimensions of a ferroic crystal sample impose existence of domains. The walls, between two adjacent domains with opposite polarizations or deformations can be defined by the symmetry change between “para” phase and “ferro” phase. But even with these “permissible walls”, the domain textures obtained only with variations of temperature will depend on their dynamic and on the sample dimensions: from one or two, to a great number of domain walls. These walls may interact together. Furthermore, any disorientation of the wall related to the permissible orientation creates imperfections (dislocations, quasi-dislocations, disinclinations) which can play a major role for the sample properties, as illustrated with an example in a simple case of symmetry change.