Thought sedans were hardtops. Did you mean convertibles (retractable hardtops)? I have one, a ‘57 Ford Skyliner.
A “hardtop” in industry parlance is a car that has A-pillars (windshield) and C-pillars (rear window), but no B-pillars (between front and rear side windows). It can be either a 2- or 4-door, but it isn’t necessarily a convertible.