The invention relates to a device for covering a surface such as a swimming pool, a sports field, a glazed surface, a vehicle body, including: (a) a drum rotatingly mounted and capable of winding or unwinding a cover, said drum being mounted on longitudinal translation mechanisms including rails provided on either side of said surface; (b) an attachment system for said cover at one transverse end of the surface to be covered so that the translation and the rotation of the drum results in the winding/unwinding of the cover above the surface to be covered; (c) a system for continuously locking the longitudinal edges of the cover onto said rails that is progressively fitted during the unwinding operation.