The work reassumes the fundamental phases, in reference to the historical changes, of the conceptions related to the restoration and to the maintenance of the architectural works of art. It is opportune to reassume the evolution of the methods and the techniques applied to the restoration of the aforesaid manufactured articles, also in relationship to the theoretical conceptions. The explication of the routine of restoration has concerned particularly the actual applications. Close to the theory and to the routine of the restoration it has been set in evidence the development of the concept of "maintenance", understood as preliminary and complementary to the restoration itself: such concept has been express referring to the Charters of restoration from the beginning of the last century to today. It is intended, therefore, to follow a historical-critical path conceived in the different, and also complementary, phases of historical, aesthetical and technological development.