The Oldsmobile and the Buick side door frame openings feature a unique modular build sub-assembly design. This design improves manufacturing quality. The door frame openings are composed of numerous individual components that are pre-assembled. The components are then attached to the vehicle as a single unit.

The center pillar serves as a rear window frame betweeen the roof rail and the belt-line of the quarter panel at the lock pilllar. The center pillar consists of an inner and outer panel which should be replaced at the factory seams if damaged.