MUFFLES AND PARTS THEREOF; RETORTS AND PARTS THEREOF; HEARTHS AND PARTS THEREOF; OVENS AND PARTS THEREOF; RECUPERATORS AND PARTS THEREOF; REGENERATORS AND PARTS THEREOF; AIR AND GAS HEATERS AND PARTS THEREOF; COMBUSTION CHAMBERS AND PARTS THEREOF; FURNACE ARCHES; FURNACE ROOFS; FURNACE LIDS; FURNACE-LID-SECTION SHAPES; SECTION SHAPES FOR COMBUSTION CHAMBERS; BLOCKS OF A SHAPE OR FORM TO PROVIDE FOR FORMING COMBUSTION PORTS; FURNACE TUYERS; RECUPERATOR TUBES; RECUPERATOR BLOCKS; REGENERATOR BLOCKS; REFRACTORY CYLINDERS; REFRACTORY CYLINDER SECTIONS; SAGGERS; KILN-CAR TOPS; REFRACTORY POTS; RABBLES OF A REFRACTORY MATERIAL; REFRACTORY TUBES FOR USE IN FURNACES; PYROMETER-PROTECTION TUBES; FURNACE LININGS; FURNACE-LINING BLOCKS; KILNLING BLOCKS; CUPOLA BLOCKS; GAS-GENERATOR BLOCKS; AIR-COOLED FURNACE-LINING BLOCKS; SUSPENDED FURNACE-ARCH BLOCKS; HEARTH-SUPPORT BLOCKS; COMBUSTION TUBES; BURNER BLOCKS; BAFFLE BLOCKS; FURNACE-WALL VENEER BLOCKS, I.E., FACING BLOCKS WHICH ARE KEYED TO, INTERLOCKED WITH, OR OTHERWISE SUPPORTED AT THE FACE OF A WALL; FURNACE-ARCH VENEER BLOCKS, I.E., FACING BLOCKS WHICH ARE KEYED OR INTERLOCKED OR OTHERWISE SECURED TO THE FACE OF A BRICK OR OTHER ARCH TO BE PROTECTED; MUFFLE-SECTION SHAPES; RETORT-SECTION SHAPES; AND MEANS FOR SURROUNDING OR SUPPORTING WARE IN A KILN AND GENERALLY KNOWN AS KILN FURNITURE