Abstract: A device for inhibiting use of a cassette deck having a cassette chamber accessible through a chamber opening in which the device includes an elongated flat body member having a length, width and thickness adapted to be received within the chamber through the opening, a transverse member at one end of the body member having a dimension greater than the corresponding dimension of the chamber opening to limit movement of the body member into the chamber, a lock element mounted and positioned within an opening in the body member and movable to one position to permit insertion of the body member into the cassette chamber and movable to another position to restrict outward movement of the body member; the lock element being adjustably positioned along a threaded member in the body member opening to a selected position therealong.