In the film noir classic 'Double Indemnity', the writers Billy Wilder and Raymond Chandler needed to resolve a particular conceit in the plot where the femme fatale shows up at the doomed hero's apartment but needs to be hidden from an occupant inside. They decided to use an outward-opening door.

This small detail has caused much discussion ever since, a good example is here: http://jpgamboa.com/archives/1424