through the accept outlet 7 according to the invention the screen structure 5 a of the dividing wall 5 has profiling on the side facing the suspension feed 3 and the reject outlet 4 so that turbulence is generated in the pulp suspension fs flowing onto the screen structure 5 a this turbulence pulls any fibers adhering to the slots or perforations in the screen structure 5 a and any other solids which could clog it away from the screen structure 5 a so that these substances can be removed with the overflow ul of the pulp suspension from the reject outlet 4 the overflow ul is equivalent to the reject in a single stage screen which is that part of the pulp suspension that contains fibers of unsuitable length and dirt particles and is either removed or recycled for further screening the overflow ul can be controlled by a flow control element 11 u2032 at the reject outlet 4 the dividing wall 5 with its screen structure 5 a is shown as a level surface in this embodiment however curved surfaces etc can also be used here furthermore the dividing wall descends at an angle in relation to the flow direction of the pulp suspension the accept chamber 6 and the accept outlet 7 are located above the reject outlet 4 so that any dirt particles present can easily be discharged downwards with the overflow.