Abstract: An apparatus for longitudinally slitting travelling webs of paper and the like is described. The apparatus includes a cutter unit having at least one slitting knife which is adjustable transversely of the path of a web through the apparatus and which can be locked pneumatically in an adjusted position. The apparatus also includes take-up means for winding into rolls, strips of paper and the like formed by slitting the web, and a web clamping assembly disposed in advance of the take-up means. The take-up means includes a mandrel and pneumatic means for clamping the leading portions of strips to be wound onto the mandrel. The clamping assembly is used to assist threading up of the web to the mandrel.