A-pillar
Automobiles
An SUV with four pillars
A
Barracuda
fastback has only two pillars
A stretch
limo with five pillars
An A pillar is a name applied by car stylists and enthusiasts to the shaft of material that supports the windshield (windscreen) on either of the windshield frame sides. By denoting this structural member as the "A" pillar, and each successive vertical support is named after a successive letter in the alphabet (B pillar, C pillar etc.) the name allows those interested in car design to have a point of reference when discussing design elements.
When looking at the side of a vehicle, the A-pillar is the pillar that attaches to the windshield and supports the roof. The B-pillar is the second post supporting the roof, and so on towards the rear of the vehicle. In the most usual configuration, the C-pillar attaches to the rear window, however, depending on configuration, the final pillar can be B, D, or even higher in more extreme examples.