D-pillar
The vertical support dividing a car's rear windscreen from its rear window (where the car has a central side window between the front and rear side windows; see C-pillar).
D-pillar: the rear frame post between back windows
The D-pillar is the vertical structural member positioned between a car's rear windscreen and rear side window. It exists only on vehicles with a central side window, creating a three-window configuration on each flank: front door glass, middle window, and rear window. On simpler body styles without a middle window, there is no D-pillar; the rear window connects directly to the C-pillar.
D-pillars are found on sedan and wagon bodies where the side glass is divided into distinct panes. The pillar supports the body frame and contributes to torsional rigidity of the chassis. Like other pillars, it carries welded joints to the roof line and the rear quarter panel, and it must be substantial enough to maintain crash safety ratings without adding excessive weight. The thickness and cross-sectional profile vary with vehicle class and platform design.
The D-pillar typically requires reinforcement around door hinge points and lock strikers on vehicles where the middle window is hinged or sliding. Weatherstripping applied to the pillar edges seals the gap between glass panes. Visibility past the D-pillar can be a constraint in design, particularly for rear three-quarter sight lines, which is why some models taper the pillar or use a thinner profile glass mounting.
In crash analysis and body repair, the D-pillar is treated as a main load path. Damage requiring replacement usually involves cutting and welding the pillar to the roof and quarter panel, a structural repair that demands jig accuracy and proper panel alignment to restore the vehicle's crash performance. Corrosion often initiates at welded seams where the pillar joins adjoining panels, making drainage hole clearance important in long-term durability.
The naming convention follows the alphabetic sequence of main pillars from front to rear: A-pillar (windscreen support), B-pillar (front door), C-pillar (rear window support on two-window cars), and D-pillar. Four-window body styles are relatively common in passenger cars and compact SUVs, making the D-pillar familiar to body technicians and automotive engineers, though it is absent in simpler coupes and many SUV designs.