Abstract: A tensible shipping container reinforcement bar having connectors on each end thereof the ends adapted to attach to diagonally opposite corner fittings of shipping containers. The bar having a compressor device capable of expansion located at a point intermediate in the bar so that when the ends of the bar are attached to diagonally opposite corners, the bar is expanded under tension. The bar is designed to prevent warping of the walls and end of the shipping containers when containers are subjected to high stress forces placed on them due to motion of containers in shipping, especially in ships. In a preferred embodiment the bar includes a device for adjusting the degree of tension provided by the bar.