Abstract: Headbox for a paper machine having a feed part, a central part extending across the machine width, and a nozzle. The nozzle extends across the machine width and has at least one continuous wall that runs across the machine width transverse to the lengthwise flow. For absorbing and discharging nozzle expansion forces in a sectional manner, several separate individual support devices distributed across the machine width for influencing the nozzle aperture are attached to the at least one, preferably continuous wall. The resulting lines of force of each support device remain at least substantially in a plane lying perpendicular to the direction of the machine width and in the flow direction, and the corresponding supporting forces individually, at least substantially, are directed to and absorbed in the central part in the plane of the flow direction.