a large round baler is equipped with a device for wrapping a bale formed in the baling chamber of the baler with a web of plastic sheeting or net wrapping medium . a supply roll of the wrapping medium is located in a box mounted forward of the baling chamber for movement along a fore - and - aft extending guide rail between a standby position , wherein a free end of the wrapping medium is supported by a guide surface at a location spaced forward of the baling chamber , and a wrapping position , wherein the free end of the wrapping medium is located for being grabbed by rotating rollers and / or the formed bale so that a length of the wrapping medium is pulled from the supply roll as it is wrapped about the bale . a power operated brake operates on the supply roll so as to provide a constant tension in the wrapping medium during wrapping operation .