So when is a closet door not a closet door? When it's a bookcase, of course, which is exactly the situation with the Hide-A-Door Bookshelf, manufactured by Space X Doors. The Space X Hide-A-Door Bookshelf is cross between a bi-fold closet door and a bookcase. In the closed position, you have a functional solid wood bookcase and display cabinet that appears to be just that – a solid bookcase. But then slide it open on its concealed tracks, and you have access to the room behind it. Hide-A-Door Bookshelves offer an unusual solution for a number of different remodeling and new construction situations. Since the bookcase completely and effectively conceals the doorway and room behind it, it's great for concealing hidden vault rooms, gun storage, secret passageways, wine storage, or ev...