A device (1) is used for introducing a running material web (3) into a tenter machine. The device (1) comprises at least one tiltable cheek (12) which receives the material web (3). This cheek (12) is tilted by at least one control element (13) by means of at least one actuator (19). This control element (13) engages on the one hand on the cheek (12) and on the other hand on the frame (17). Angle sensors (32) record the angle between the cheek (12) and the control element (13) as well as between the frame (17) and the control element (13). These angles are delivered to calculation means (66′) for calculating the difference of the two recorded angles.