A herculite door was a particular manufacturer of a frameless glass door. This would normally consist of 1/2" tempered glass with the vertical edges polished. Tops and bottoms are pivoted by either patch fittings or full width shoes, often with polished metal cladding. These are hi profile doors you might see at a lobby, or mall entrance, or perhaps an executive office. People often recognize frameless glass doors as the age old term herculite door.