Memory cartridge security locking device

The locking apparatus is used to secure one or more memory cartridges in a housing in a computer system module. An L-shaped member is fastened to the module by a screw in an existing threaded screw hole in the module. A second member is inserted into the module and locked to the L-shaped member by a padlock. The second member includes a first plate that fits into a clearance space between the cartridges and the housing to prevent the cartridges from being unplugged from connectors mounted in the housing. The second member includes a second plate that prevents the end of the outermost cartridge from being pulled out of the housing to clear the first plate and includes a third plate which in use covers the mounting screw of the L-shaped member so that the screw cannot be removed.