<P> Closed vehicles without a B - pillar are widely called hardtops and have been available in two or four - door body styles, in sedans, coupes and wagons . Designs without a center or "B" pillar for roof support behind the front doors offer increased occupant visibility, while in turn requiring underbody strengthening to maintain structural rigidity . In the early 1970s, General Motors broadened their definition of "hardtop" to include models with a B - pillar although: "up to then, everybody thought a hardtop was a car without a center pillar ." </P> <P> Pillars are implied, whether they exist or not; where a design's greenhouse features a break between windows or doors without vertical support at that position, the non-existent pillar is "skipped" when naming the other pillars . Thus a two - door hardtop or a three box designed coupé could have its rearmost pillar called the C - pillar even in the absence of a B - pillar . Conversely additional doors, such as on limousines, will create additional B - pillars; the B - pillars are then numbered, B1, B2, and so forth . </P> <P> In addition to the pillar nomenclature derived from viewing an automobile in profile, some older cars have a two - part windshield or a split rear window, with the two halves separated by a pillar . Posts for quarter windows (a smaller window typically between the front window and the windshield) are not considered a named pillar . </P> <Ul> <Li> <P> A photographic typology illustrating variations of the design of the C - pillar </P> </Li> <Li> <P> The B or center pillar between the front and rear doors on an AMC Concord station wagon </P> </Li> <Li> <P> From left to right: C, B2, B1, and A-pillars, with small quarter glass in both doors (AMC Ambassador) </P> </Li> <Li> <P> A Lincoln Town Car with five pillars (A, B1, B2, B3, and C) </P> </Li> <Li> <P> An accident due in part to an A-pillar blind - spot </P> </Li> </Ul>

What is a b pillar on a car