In a paper or board machine drying line after the wire section, during dewatering a web's (W) width is affected in a direction crosswise to the web's traveling direction. Starting from an edge, at least one device (20A, 20B) brings about a force effect of a desired magnitude which is directed all the way to a desired arbitrary crosswise web position in order to modify web characteristics. A device in a paper or board machine line after the wire section has means for processing the web and for dewatering. The paper or board machine line after the wire section further has at least one device (20A; 20B) for directing a force effect at a desired partial area (WS) of the web (W) in the cross machine direction in order to modify the web's characteristics profile in the cross machine direction.