A paper-making assembly has a drum with a pivoting (22) inner pressure seal (20) in contact with the moving inner surface (12) and separating two zones of different pressure (P1, P2). The pivot point (22) and associated rocking interface (26) are esp. variable (VR) with respect to the drum inner surface (12). The pivot point (22) forms part of a fixed strip (28) which is transverse to the direction of rotation (L) and is clamped in the required position by a piston or pneumatic hose. The fixed strip has spacers which are adjustable in the end-position.
