In furnace of this type, water-cooled rollers through a long, straight heating unit move the workpieces. These are extensively used in the heat-treating of plates and other types of workpieces and, more recently, for reheating slabs immediately after they have been continuously cast. A furnace of this type, with a high thermal head, is used to heat slabs prior to their reduction in a planetary mill. Main burners above and below the pass line heat the slab through the top and bottom surfaces and auxiliary burners fire through the sidewalls in line with the slab edges to supply additional heat to the edges and corners. It has the ability to handle very long workpieces with little danger of mechanical damage. Skid marks are avoided due to the uniform motion of the workpiece through the furnace or a back-and-forth rocking motion produced by the rollers.