a molded plastic load center enclosure allows the circuit breakers contained therein to be compactly aligned on one side of the enclosure . depressions formed within the bottom of the interior surface of the enclosure produce bosses extending from the exterior surface thereof , which provide a cooling air circulatory space between the enclosure and a support wall . metal disks inserted within the depressions provide increased thermal capacity to the enclosure interior while allowing the use of explosive charge - driven nails to attach the enclosure to the support wall without damaging the plastic material .