Body in white

Body in white or BIW refers to the stage in automotive design or automobile manufacturing in which a car body's sheet metal components have been welded together — but before moving parts (doors, hoods, and deck lids as well as fenders), the motor, chassis sub-assemblies, or trim (glass, seats, upholstery, electronics, etc.) have been added and before painting.

The name derives from manufacturing practices before steel unibody or monocoque bodies — when automobile bodies were made by outside firms on a separate chassis with an engine, suspension, and fenders attached. The manufacturers built or purchased wooden bodies (with thin, non-structural metal sheets on the outside) to bolt onto the frame. The bodies were painted white prior to the final color.

A folk etymology for Body in White suggests the term derives from the appearance of a car body after it is dipped into a white bath of primer (undercoat paint)— despite the primer's actual gray color. This could also refer to when car bodywork would be made of timber - all timber products, furniture etc, are considered to be "in the white" when at the stage of raw timber before finishing/varnishing.