In order to securely hold a moving belt of a continuous casting device against selective movable side walls, a first group of rotatable control rods which are disposed in a first supply header and an adjacent exhaust header are arranged to produce narrow high pressure zones in the film defined between the cooling pad in which the header are formed and the moving belt. These zones can be selectively moved to juxtapose the side walls when the gap between the walls is adjusted. A second group of rotatable control rods which are disposed in second and third supply headers selectively heat the side edges of the belt which are relatively cool as compared with the center section which is exposed to molten metal. As the side walls are moved apart the width of the edge sections which are exposed to pre-heated coolant can be reduced and the amount of normal temperature coolant applied thereto also increased.