Abstract: A supplementary deck which is easy to mount and dismantle between the existing decks in ships of the kind intended to carry loading containers and wherein at least one of the decks is provided with apertures, arranged in groups of four, which aperture groups are distributed equally pitched over the deck to receive locking bolts of the kind known as twist locks which serve to removably secure the loading containers to the deck. The supplementary deck comprises a number of wall sections each one of which is formed at the top and at the bottom with apertures, arranged in groups of four for reception therein of locking bolts and they are disposed in the same pitch relationship as the apertures formed in the stationary deck. The wall sections are arranged to be connected in pairs at their top to rectangular loading container platforms by means of the locking bolts. The platforms are provided at each one of the lower corners with an aperture for passage therethrough of a locking bolt.