The present invention pertains to a method for producing slabs of steel, whereby the rod leaves an ingot mould together with the liquid fusion contained therein, while, in a casting guide installed downstream from said ingot mould, the jaw aperture of the scaffold-type guide rolls is progressively adjusted by means of elements connecting the lower and the upper frames. The inventive method comprises the following steps: a) changing the jaw aperture by swaying the device around a centerline (c) in such a way that the dynamic effects on the guide rolls are insignificant; b) adjusting the sway amplitude (A) of the jaw aperture to such a value that no plastic deformation of the ingolt mould can result therefrom; c) determining the actual jaw aperture (s); d) determining at the same time the actuating power (F) of said adjusting elements, as well as the amplitude (A) of said actuating power; and e) in the event of an increased actuating power amplitude (A), adjusting the jaw aperture (s) based on a measure which is set and/or guided by pressure control on at least one adjusting element.