Schaum''s Outline of Optics, Mc-Graw-Hill

A self-supporting container is removably mounted on a truck for transportation to and from a support surface, the truck having jacks thereon for transferring the container between the support surface and the truck, and the container having two pairs of retractable leg assemblies for supporting itself upon the support surface, each leg assembly including a horizontally pivotable housing and a vertically pivotable leg, and being shiftable between a storage configuration with the housing and the leg extending longitudinally alongside the container and an intermediate configuration with the housing extending laterally outwardly of the container and the leg hanging downwardly from the housing. In transferring the container from the truck to the support surface, the container is raised by the jacks and the leg assemblies are shifted from their storage configurations to their intermediate configurations, then the container is lowered until the legs contact the support surface whereupon elongated pivot pin slots in each leg accommodate the downward vertical movement of the housings with respect to the legs to a supporting configuration wherein abutment surfaces on the leg assemblies and the container cooperate to lock the leg assemblies against any further movement until the container is raised from the support surface.