A shipping container support mechanism for a rail freight wagon is adjustable between a retracted position in which a container can be supported in a well of the wagon between elevated end platforms which extend over wheels and bogies. In the deployed, extended position, the mechanism supports an end region of a container, the opposite end of which can be supported on another such mechanism or an end platform. The support mechanism is mountable in the side wall of the wagon and has a pivotal support arm which can move from a stowed position in the wagon frame to a horizontally extended position.