In order to allow create a precise technical drawings, it is important to be able to draw 3D models of machine parts, which form the basis for further work in the CAD/CAM systems. The advantage of modelling and the creation of the underlying sketches lies in the simplification of control, i.e. using all the assembly features and icons are mostly single-level, creating a much better idea to work, unlike some other CAD systems. After creating a two dimensional sketch, it is possible to get into the 3D interface through the function "Exit Workbench" in modules PART DESIGN, SHAPE DESIGN, etc. In 3D interface, then we use the resulting functions which create PART or parts of the Product, which we can join in the module ASSEMBLY DESIGN. Advantage of CATIA is its simplicity.Icons are placed directly on the sides of the active desktop, or you can activate them via the main menu View Toolbars. This structure of the whole system is necessary, in view of the scope and job opportunities CATIA.Moreover, CATIA can also do conversion with the documentation created in older CAD systems (e.g. AutoCAD DWG format) directly in special module INTERACTIVE DRAFTING).