a first positionable roll which guides the endless web directly to an additional positionable roll with a predetermined wrap angle on each positionable roll, shafts of said positionable rolls lying parallel to one another in a plane and being held by a frame;

the web being fed to and led away from the positionable rolls via a respective first stationary roll and a respective additional stationary roll;

the frame being pivotable relative to the stationary rolls about a first axis of rotation which is substantially perpendicular to said plane in order to modify a position of an edge of the web;

the frame being pivotable relative to the stationary rolls about a second axis of rotation parallel to a movement direction of the web between the first and additional positionable rolls with an actuated adjustment device that is actuated by at least one of the functions selected from the group consisting of manually, electrically, hydraulically, and pneumatically to make said web rigid to prevent sagging; and

along the web there is situated at least one sensor that acquires a sagging comprising a movement in a direction perpendicular to a plane of the web at one side of the web and indicates it via a control device, and in which, dependent on the indication, the frame is pivoted about the second axis of rotation.