Abstract: A high temperature car bottom furnace is provided with an improved seal on the mating closing surfaces. The side walls of the furnace chamber have tapered bottom surfaces sloping toward the end wall of the furnace chamber. The moving furnace floor is provided with complementary tapered sealing surfaces mating with the bottom surfaces of the side wall. A resilient compressible insulating layer is secured therebetween for sealing the chamber along each side wall. This arrangement not only reduces the abrasive contact between the moving surface and the compressible insulating layer but also facilitates non-abrasive closing action by the door wall of the furnace.