Abstract: This invention relates to a method of and apparatus for the positioning of thick slabs (2) to be introduced into a furnace, particularly into a walking-beam furnace, the positioning being effected with the aid of optical devices (5, 9, 10) and electronic devices (11, 12). By this method, at each lateral region opposite the furnace mouth (3), onto the upper surface of a slab (2) and at the region of its end faces (102, 102'), there are projected at least two blades of light (6, 7, 8) of a given length, which are normal to the direction of entrance and advance into the furnace and parallel to each other, the ends of which are perfectly aligned on a straight line which is parallel to the direction of entrance and advance into the furnace, the blades (6, 7, 8) producing parallel lines of light (106, 107, 108) on the surface of the slab (2), the lines being interrupted at the end edges (102, 102') of the slab.