In this book, the Orthographic System of representation is presented and explained. First, the main elements of any representation (points, straight lines and planes), are represented by means of their projections, according to the basic rules of the system.Secondly, the relationships between the elements (intersections, parallelism and perpendicularity), are calculated or imposed. Finally, the essential methods of abasement, turn and plane change are explained and applied to calculate true magnitudes, distances and angles within the elements and also with regard to the projection planes