to the container 2 by forcibly inserting the hooks into the orifices in order to avoid having the reinforcement bars accidentally release from the container when there is a displacement in vertical alignment between the top side of the container with respect to the bottom side of the container we employ in our preferred embodiment of the invention a tensioning means 18 such as that shown in fig2 and or fig8 and 9 wherein the reinforcement bar 16 is installed while it is under tension the degree of tension in the reinforcement bar 16 being approximately half the amount of tension and expansion of bar 16 that is provided by tensioning means 18 in this respect the bar is caused to extend to its maximum extension due to a straightening out of the curvature of tensioning means 18 and the elasticity inherent in such a reinforcement bar 16 must be taken into account the shortening of the opposite diagonal bar will be compensated for by the pre tensioning and thus prevent the bar from being released from its intended position the connection hooks 14 can be affixed to bar 16 by welding bolting or any other conventional means in fig8 and fig9 the connecting means 14 and 44 are an integral portion of reinforcement bar 16 can be made simply by making permanent bends in the end of the bar as shown in the drawings the term connecting means 14 as used in this invention merely means for grasping or connecting the ends of the reinforcement bar 16 on to the side wall of an orifice of a corner fitting of a container it can simply be a projection 14 extending perpendicularly from bar 16.