Apparatus which is capable of providing efficient cooling of rack mounted electronic modules while accommodating relatively large tolerances in the mounting of the modules. A plurality of thermally conductive sliding wedge blocks are interposed between the lower surface of each module and the upper surface of the cold plate base of the rack. The mechanism for clamping a module to the rack also pulls the wedge blocks together to fill in the gap between the lower surface of the module and the upper surface of the cold plate so as to provide a complete thermal path therebetween.