A Dutch door (American English), or stable door (British English), or half door (Hiberno English), is a door divided horizontally in such a fashion that the bottom half may remain shut while the top half opens. The initial purpose of this door was to keep animals out of farmhouses, while allowing light and air to filter through the open top. Later modifications included doors where both halves can be closed or opened together. Mr. Ed's door from the show of the same name is an example.
Dutch doors are often used in North-American passenger train cars to allow crewmen to interact safely with other employees not aboard their trains (or simply to visually inspect their own train) without risking falling from the train. Recent operating rules changes in Canada have rendered the dutch-doors obsolete, although legacy rolling stock retains the doors.
The term is also applied to the modified rear doors on selected GMC Safaris and Chevrolet Astros that have a flip up rear window and two small half-size doors underneath.