A Dutch door or stable door (British English

British English

British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

), or half door (Hiberno English), is a door

Door

A door is a movable structure used to open and close off an entrance, typically consisting of a panel that swings on hinges or that slides or rotates inside of a space....

 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

Rolling stock

Rolling stock comprises all the vehicles that move on a railway. It usually includes both powered and unpowered vehicles, for example locomotives, railroad cars, coaches and wagons...

 retains the doors.

The term is also applied to the modified rear doors on selected GMC Safaris and Chevrolet Astro

Chevrolet Astro

The Chevrolet Astro was a rear-wheel drive mid-sized van introduced by Chevrolet in 1985 to rival domestic competitors the Dodge Caravan/Plymouth Voyager twins and the Japanese Toyota Van. Also sharing the Astro's platform was its sibling, the GMC Safari...

s that have a flip up rear window and two small half-size doors underneath.