A hardtop is a body style that differentiates a sedan from other types of automobile designs with a steel roof. In a hardtop model, there is no pillar or post in the center of the side window openings when the windows are rolled down. The area is completely wide open and free of anything from the edge of the windshield or wing window to the rear window. In a post-style or sedan, there is a dividing pillar behind the front door, and in four-door models there is a pillar and post where the two doors meet, which goes up to the roof line.
In the 1950s, Ford Motor Company designed and sold a hardtop convertible that utilized a retractable hardtop roof that was stored in the trunk area. When a switch was pushed to activate the retractable roof, the trunk opened from the rear window up and the hardtop was drawn into the waiting receptacle. Once inside, the trunk once again closed and the vehicle was a topless convertible. These vehicles were prone to frequent problems from the unsophisticated technology of the era and were only produced for a short while.
While the majority of hardtop models were two-door automobiles, there were several models of four-door hardtop vehicles offered for sale. The generous sizing of the vehicle designs of the early 1950s and 1960s created problems for this option of hardtop automobile. Far too often, the rear doors of the four-door hardtop models would develop a sag. The extremely heavy doors were mounted to a half pillar that serves both as a latching pillar for the front doors and a hinge pillar for the rear doors. With one end of the pillar standing free, gravity soon waged war on the post's integrity.
The weight of the rear doors along with the sideways motion from slamming the front doors soon caused the half pillars to weaken and wobble. This led to poorly-closing front doors as well as doors that would actually pop open while the vehicle was in motion. Although several modifications in the design of the pillar were completed, it was not until vehicles constructed with a unit body, often called uni-body, were manufactured that the pillar became strong enough to last the lifetime of the vehicle with virtually no problems.
Traditionally known as a sportier option, the pillar-less top design offered a new styling trend in a previously neglected area of the automobile. American models such as Oldsmobile and Lincoln pushed the option as having more class than a traditional top. Brands such as Chevrolet that were known as utilitarian vehicles boasted roominess and style comparable with the more luxurious models.