a self - propelled forage harvester is equipped with a crop gathering device which transports crop material from the ground to feed rolls that position the crop for being chopped into small pieces by a chopper drum . to prevent pieces of crop material from accumulating on top of the housing structure for the feed rolls and the chopper drum , a flexible shield is mounted between the bottom of the operator &# 39 ; s cab and the top of the crop gathering device . various different access elements of the shield may be quickly opened to provide access to the feed rolls , chopper drum and other functioning elements provided for processing the crop .