For producing a protective layer made of a sheet, a device exhibits an oblong guide element (1) with an upper edge (2), by way of which a sheet (7) can be folded in its longitudinal direction. Clamping elements (15, 16), designed as sliders, are arranged on the side of the guide element (1); and the sheet (7), folded in its longitudinal direction, can be grasped on both sides of the guide element (1) with said clamping elements. To form folds in the sheet (7), the clamping elements (15, 16) can be slid in the longitudinal direction of the guide element (1).