Mild Steel Window Doors. Window doors can be used on the front or rear of ProLine frames to provide viewing of electronic equipment. They have 130-degree hidden hinges and a flush bezel latch (PFBS) that operates a 3-point latching mechanism. Doors have a clear safety glass window. Window Door Type: Steel and Safety Glass. Foam-in-place, urethane gaskets for door and window provide optimum sealing. Install easily on front or rear of enclosure frame; can be hinged on left or right. Fits only back of double-bay frame, front and back of single-bay frame 6 mm thick window that provides maximum protection and viewing area.