A method includes manufacturing a sheet-type substrate having a security thread in which a security thread having features spaced apart from one another in the longitudinal direction of the security thread is inserted into the substrate in such a way that it is at least partially embedded in the substrate. At least one of the features is displayed as an image after the embedding of the security thread. The stretch of the embedded security thread in the longitudinal direction is calculated based on the image of the at least one feature, and the region of the substrate in which the calculated stretch of the security thread exceeds a specified maximum stretch is obliterated depending on the calculated stretch.