1. A latch mechanism for releasable securement of a freight container on a support pedestal in position for transportation by a carrier vehicle and comprising, in combination: catch means on said container and having side, bottom and catch surfaces at the lower region of the container, said pedestal having container supporting and retaining surfaces relative to which the contaier is carried in sue, a clasp member hingedly mounted on one of the retaining surfaces of said pedestal for switnging movements to and from positions of retaining engagement with said catch surface of the catch means when the container is supported on said supporting surface of the pedestal, said clasp member having a cam surface which has a steep incline relative to said one of the retaining surfaces and which overlies said catch surface when the container is supported on the pedestal, said clasp member also having a detent surface normally disposed in agnular relationship to said one of the retaining surfaces and disposed in opposed relationship to said cam surface for engagement with said catch means when the container is moveD into supported position on said pedestal to deflect the clasp member away from the catch means until the cam surface is in position for engagement with said catch surface, and resilient means for biasing said clasp member toward said position of retaining engagement with said catch surface, the biasing force of said resilient means and the angularity of said cam surface relative to said catch surface being effective to require a large force for effecting release of said clasp member from said catch surface as a result of force applied by the catch surface to the cam surface in a direction parallel to said one of the retaining surfaces.

11. A railway flat car comprising a deck, a plurality of container supports on the deck, a container having lower corners supported on the container supports, each of said lower corners having an opening therein, each container support having a generally horizontal seat to support the associated lower corner of the container, and a pair of connected walls arranged in a right angular relation and extending upwardly from the seat to restrain the container against horizontal movement, a releasable locking member on each container support adjacent one of the walls, means mounting the locking member for generally pivotal movement about a generally horizontal axis, the upper portion of said locking Member having a protuberance extending inwardly from one of the walls and adapted to extend into the adjacent container opening for restraining the container against removal from the associated support at a lifting force below a predetermined minimum lifting force, and means urging the upper portion of the locking member and protuberance inwardly toward the container opening, said protuberance having a lower cam surface for contacting an edge of the container corner defining the lower portion of the associated container opening and a downwardly inclined upper surface adapted to contact the lower corner of the container upon lowering of the container onto the container support, the contact of said container with said upper surface upon lowering of the container urging the locking member outwardly for seating of the container on the support, and upward movement of the container being restrained by said protuberance until a predetermined minimum upward force is reached whereupon said protuberance is urged outwardly by contact of said lower cam surface with the edge of the container corner defining the opening.