A car`s body is categorized according to the number of doors it has, the arrangement of its seats and the structure of its roof. A car`s roof is supported by pillars on each side of the car`s body, while convertible models are equipped with retractable fabric tops that rely on the pillar at the side of the windshield for upper body strength. Other aspects of this like the convertible mechanisms and the glass areas are basically non structural, though an increase in the latter is preferred by many for aesthetic reasons.

Car bodies usually have designs that last for three to six year cycles for it is impractical and highly expensive to come up with totally new concepts every year. A car manufacturer usually spends as much as three to four years to plan and purchase new equipment for a new auto body design, aided by recent computer design software.

The car body is attached to the car chassis during the manufacturing process, and together absorbs the reaction and the forces from the movements of the axle and the engine of the car. The two also receives the forces from the wheels during acceleration and braking, absorbs wind forces aerodynamically and sustains road shocks through the suspension. Figuratively, one can compare the car body to the carapace of an insect. It protects the car`s precious occupants from major damage during an accident or collision.

Recently, body mechanical and trim for some cars are customized for different purposes. Some modern cars have a combined chassis and body. This arrangement needs special reinforcement of the body though, for it to be able to resist the amount of forces applied to it. These cars can be easily spotted by the inclusion of special braces for structural strength. Other customization include, noise reduction and isolation and the use of high-gauge steel components.