Abstract: An anti-theft locking device for securing computer-related units against unauthorized removal from a work station utilizes a base frame anchored to a work surface at the work station and constructed to receive one of the units in nested position so as to preclude movement of the unit in directions parallel to the work surface and to receive a hold-down frame placed over the units and secured to the base frame with screw-type locking mechanisms extending into the base frame beneath the nested unit to protect the screw-type locking mechanisms from tampering and to conserve space at the work station.