Abstract: A device for aligning material webs which in a longitudinal direction have alternating regions of differing thickness, has a top and a bottom aligning rail, which are disposed substantially at right angles to the material web and opposite one another with slight clearance. The top aligning rail has a row of aligning elements which are disposed in a longitudinal direction of the aligning rail. They are supported so as to be movable substantially at right angles to the plane of the material web and may be brought to rest on the bottom aligning rail with the material web for alignment lying in between. The aligning elements are supported in a substantially freely movable manner in the top aligning rail such that they may be brought under the action of gravity to rest on the material web. The aligning elements after being brought to rest on the material web are releasably fixable in the top aligning rail.