Method of controlling a reheat furnace for reheating iron and steel products, for example slabs, blooms, ingots or billets, making it possible for the product to be reheated to be brought to the desired temperature for rolling, the furnace being equipped with a heat recuperator. Upon receiving print data and a characteristic value from an external device, the image forming apparatus stores the print data into a storage area which has been allocated the same characteristic value as the received characteristic value. The abutment or counterabutment surface may be arranged on a transversely deformable, resilient engaging element which engages the corresponding surface in tension. Thus, a focal point of the X-ray tube device can be moved directly above the foot side end of the X-ray image detector.