Method for marking a material defect in a sheet material, with the steps: - sensing a material defect in a moving sheet material by means of a defect sensor, - sensing at least one surface structure feature in the region of the sensed material defect using a first marking sensor and determining of a structure data record representing the surface structure feature, - storing the structure data record, - wherein, after the storing of the structure data record, - the surface structure feature is sensed by a second marking sensor following the first marking sensor and a second structure data record representing the surface structure feature is determined, - the position of the defect on the sheet material is identified by a comparison of the stored first structure data record with the second determined structure data record, and - if the structure data records match, a processing unit is actuated, which then processes the sheet material in the region of the material defect, characterised in that - between the first and second marking sensor (4a, 4b), an input sensor senses the surface structure feature of the sheet material, before a second processing unit changes the surface structure of the sheet material, - from the surface structure feature which is sensed, an input data record is produced and compared with the first structure data record, and - if the first structure data record and the input data record match, an output sensor senses the surface structure feature of the sheet material emerging from the second processing station, taking account of the run-through speed of the sheet material through the second processing unit, and an output data record is determined and stored. - sensing a material defect in a moving sheet material by means of a defect sensor, - sensing at least one surface structure feature in the region of the sensed material defect using a first marking sensor and determining of a structure data record representing the surface structure feature, - storing the structure data record, - wherein, after the storing of the structure data record, - the surface structure feature is sensed by a second marking sensor following the first marking sensor and a second structure data record representing the surface structure feature is determined, - the position of the defect on the sheet material is identified by a comparison of the stored first structure data record with the second determined structure data record, and - if the structure data records match, a processing unit is actuated, which then processes the sheet material in the region of the material defect, characterised in that - between the first and second marking sensor (4a, 4b), an input sensor senses the surface structure feature of the sheet material, before a second processing unit changes the surface structure of the sheet material, - from the surface structure feature which is sensed, an input data record is produced and compared with the first structure data record, and - if the first structure data record and the input data record match, an output sensor senses the surface structure feature of the sheet material emerging from the second processing station, taking account of the run-through speed of the sheet material through the second processing unit, and an output data record is determined and stored.