Abstract: A headbox for a machine for producing a fibrous material web, in particular a paper or cardboard web, includes: a central assembly preferably forming the carrier elements of a turbulence generator, said assembly having a table leaf on the bottom side; and a headbox nozzle adjoining directly downstream in the machine running direction and extending in the machine transverse direction, said nozzle comprising at least one lower and one upper continuous nozzle wall extending over the machine width. The lower nozzle wall of the headbox nozzle of the headbox includes a lower lip plate, in particular a lower lip carrier plate, which is connected, in particular welded, to the table leaf of the central assembly by means of ribs extending in the machine running direction and spaced apart in the machine transverse direction. The ribs are designed in an elastic or pliable manner in the machine transverse direction.