Abstract: High density, rapid access storage of cassette modules is provided by way of a storage unit in which the modules are supported in side by side edge-on orientation, being supported at the diagonally opposed front top and rear lower corners, and having freedom for lateral sliding movement while thus secured within the storage unit to afford finder access to a selected cassette, and to permit insertion and removal by handfulls. Release of a selected cassette is readily effected by upward raising of the cassette within a top clearance space provided thereover, thus freeing the rear lower corner from the storage unit, for frontal withdrawal of the cassette module from the storage unit.