Abstract: A module is sandwiched between an underlying member and a superimposed enclosure. The underlying member may be a base or another enclosure. The module is constructed so that it can be secured to the underlying member. The superimposed member has feet formed with horizontal grooves which fit into pockets in corners of the module. A slide is horizontally movable in the module between retracted position and an operative position. In the operative position edges of the slide engage in the grooves in the feet to lock the superimposed enclosure to the module and thereby to the underlying member. The slide may be detachably secured in operative position.