Abstract: A maximum density mobile storage system in which groups of racks or other storage devices are arranged side by side in a row or bay along side a loading and unloading aisle or corridor, the individual racks being selectively movable individually or in groups so as to leave a loading or unloading space between any two of the racks, whereby the length of the bay need exceed the sum of the widths of the racks by an amount which equals the width of the desired gap, particularly characterized in that the width of the gap can be varied simply by altering the position of end stops which determine the overall limits of travel of the racks; any moving rack can be stopped at any point at any time therefore enabling the establishment of multiple gaps; the racks are individually motored and the controls are such that when the system is placed in motion the racks remain in motion until all gaps in the moving direction have been filled or closed; individual controls can be carried by the associated racks or centrally posit