Abstract: A prismatic tubular brick of refractory material for constructing the checkerwork structure of regenerative furnaces, the brick having mirror image top and bottom surfaces and a central passage extending therebetween. Two pairs of opposed parallel side walls of uniform thickness having aligned recesses in the top and bottom surfaces thereof, are connected together by angle portions at their adjacent corner edges. The top and bottom surfaces of the angle portions are elevated with respect to the recessed top and bottom surfaces of the side walls and are of similar size and shape. Accordingly, the elevated and recessed surfaces of one brick cooperate with the elevated and recessed surfaces of another brick to interlock the bricks together in an offset stacked arrangement.