The use of computers has changed the practice of spatial representations. The users are no longer drawers but modelers who need to be able to check the coherence of models. The teaching of representations has to adapt with this evolution, especially in Schools of Architecture. A pedagogical way is to give interpretation tools of spatial representations through projective properties (incidence or affine properties) and consequence of intrinsic constraints (parallelism, orthogonality, and symmetry). The application of this knowledge is essential for the rebuilding of existing 3D objects or for a design process, with the restitution of 3D models from sketches. These approaches are illustrated in a pedagogical way, using dynamic geometry, in the restitution of the polyhedron of the engraving “Melencolia Ii of A. Dürer, and in a dynamic sketch of a skylight inspired of the Vitra museum of F. Ghery.