an apparatus for housing and cooling circuit card assemblies employed in communication and other systems is disclosed including a chassis having opposed end walls which are formed with a series of spaced inlet card guides and correspondingly spaced outlet card guides , respectively . a straight - pass heat exchanger is directly mounted to each circuit card assembly via thermally conductive material , and opposed ends of the heat exchanger are mounted by a wedge lock to respective inlet and outlet card guides . the heat exchanger employs unique angled interface geometry that creates a gasketless airtight joint with complimentary inlet and outlet card guide geometry through which cooling air passes .