The stylist responsible for the design of the exterior of the vehicle develops the proportions, shape, and surfaces of the vehicle. Interior design is first done by a series of digital or manual drawings. Progressively, drawings that are more detailed are executed and approved by appropriate layers of management. Clay (industrial plasticine) and or digital models are developed from, and along with the drawings. The data from these models are then used to create a full-sized mock-up of the final design (body in white). With three- and five-axis CNC milling machines, the clay model is first designed in a computer program and then "carved" using the machine and large amounts of clay. Even in times of high-class 3d (three dimensional) software and virtual models on power walls, the clay model is still the most important tool to evaluate the design of a car and, therefore, is used throughout the industry.