Abstract: A method for threading a material web (3) through a processing plant (1). The material web (3) is divided, by a longitudinal cut, into a first narrow part (31) and a second broad part (32), the first part (31) being passed through the processing plant (1) while the second part (32) is separated. The width of the first part (31) is increased successively so that a growing share of the material web (3) is passed through the processing plant (1). Finally the entire width of the material web (3) is passed through the processing plant (1). The material web (3) is pulled through the processing plant (1) by a controllable force (tension). The magnitude of the controllable force is automatically adjusted to the width of the first part (31) of the material web (3), preferably in such manner that the magnitude of the force is selected proportional to the width of the first part (31).