A seal assembly for sealing at least one negative or positive pressure zone which adjoins a surface which is perforated and moves in a movement direction in a machine for making paper, tissue or cardboard, has at least one sealing element which lies opposite the moving surface and is arranged in a receptacle which can be moved to change the format of the negative or positive pressure zone. In order to simplify the adjustability of the receptacle in order to position the sealing element, there is a signal transmitter which is connected directly or indirectly to the sealing element and the signal of which can be received on that side of the moving surface which faces away from the sealing element.