A picture or other work of art consisting of two equal-sized parts facing one another like the pages of a book. Diptychs are usually fairly small in size and often the two parts are hinged together so the work could be folded when not in use and easily transported. The type seems to have originated in ivory carvings in the late Roman Empire. Initially they were used for writing tablets, the outer surfaces being carved, with wax on the hollowed inner surfaces. They were sometimes used to commemorate family events such as weddings, but they were mainly used to mark the appointment of a new consul; it became the custom for the office holder to distribute such panels as gifts to friends, relatives, and persons of rank.