Headbox for paper machines or the like

A headbox for dispensing a machine-width suspension flow from a machine-width nozzle type discharge channel which is defined by two machine-width flow control walls converging on each other. Located on the downstream end is a machine-width discharge gap for the flow of suspension. One of the two flow control walls is for fine adjustment of the discharge gap width and is equipped with an elastically flexible wall section which extends across the machine width. This wall section is equipped with a number of areal heating elements in a succession across the machine width, with which material layers having different coefficients of heat expansion may be coordinated. By appropriate heating of individual heating elements it is possible to achieve a local deformation of the flexible wall section and thus a local change of the discharge gap width and a correction of the basis weight cross profile of the paper web produced.