Transom shares sunlight where no windows existed and has character! transom viewed in dentist's hallway Below is an explanation of the term 'transom' found on Wikipedia . In architecture , a transom is the term given to a transverse horizontal structural beam or bar, or to the crosspiece separating a door or the like from a window above it, as opposed to a mullion which refers to a vertical structural member. [1] Transom is also the customary U.S. word used for a transom light , the window over this crosspiece. [1] [2] In Britain , the 'transom light' above a door is usually referred to as a " fanlight " if a semi-elliptical shape, and occasionally as an "overlight" or "hopper", or by the French word "vasistas". [3] more Cool Clicks found here