A stanchion assembly is provided for retaining cargo in a hold from lateral motion, the hold having a deck grid fitting assembly and a ceiling grid fitting assembly. The stanchion assembly includes an elongated beam with a box cross section of two parallel webs and two parallel flanges. The beam is an extrusion of an aluminum or aluminum alloy. The assembly includes upper and lower end caps on the ends of the beam. A spring assembly within the elongated box beam retains the beam in a vertical position within the corresponding fitting on the grid assembly on the deck and the ceiling. The stanchion assembly has a weight no greater than 67 pounds. The stanchion assembly has a length L in the longitudinal direction from a lower end cap to an upper end cap when the spring assembly is uncompressed. The beam has a stiffness capable of resisting a design load applied to one of the webs normal to the longitudinal direction with a deflection no greater than L/90.