Checkerwork in horizontal chamber of a regeneratively fired furnace

A checkerwork in a horizontal regenerator chamber of a regeneratively fired furnace, comprising an array of horizontally and vertically adjacent hollow prismatic bricks or refractory material, each brick having a horizontally extending longitudinal axis, a rectangular periphery and an axially extending bore of rectangular cross section, the rectangular periphery of each brick defining a stepped recess extending substantially parallel to the longitudinal axis along each corner of the brick periphery, adjacent ones of the recesses in adjacent ones of the bricks engaging each other, the bore and periphery being defined by walls alternately absorbing heat from exhaust gas escaping from the furnace through the bore and transferring the heat to combustion air drawn therethrough, and the bricks being so spaced and arrayed in horizontal and vertical rows that each group of four horizontally and vertically adjacent bricks defineds not only four of said bores but an additional gas flow channel of rectangular cross section, vertical ones of said brick walls between the bores and gas flow channels being in vertical alignment whereby all vertical pressure forces exerted by an upper one of the horizontal rows of bricks upon a lower one of the rows are absorbed exclusively by the vertical brick walls while the bores and gas flow channels are free of pressure.