A hardtop is a term for a rigid, rather than canvas, automobile roof. It has been used in several contexts: detachable hardtops, retractable hardtop roofs, and the so-called pillarless hardtop body style.
Among the modern body designs is the two- or four-door hardtop that typically "does not have a center pillar" and requires additional reinforcement compared to similar sedan styles for support in rollover situations.
Read more about Hardtop: Detachable Hardtops, Pillarless Hardtops, Retractable Hardtops, Collectibility