"The artist builds a solid external shell as the body of the copter. When done, the modeler breaks up his model: he selects window areas and detaches them as new objects, followed by the area for the doors (also detached as new objects). The modeler now has open objects representing the body, windows, and doors. The modeler applies Shell to the body, and sets it to extrude both outward and inward, with the inward extrusion amount greater than the outward. Next, Shell is applied to the windows, with inward extrusion only. The modeler then copies the Shell modifier from the body to the doors, and reduces the doors' outward extrusion amount. The result is a solid body with an interior that can accept additional modeling, inset windows, and doors that are slightly less thick than the shell of the helicopter." when building a car, vehicle or any transportation equipment it is important first work on the outer shell, detach the windows and doors. Apply the shell to the