A removable cover plate to be used in a threshing module of an agricultural machine, e.g., a grain harvester. The removable cover plate provides a uniform and homogeneous distribution of grains onto a cleaning and harvesting system of the machine. The removable cover plate is designed to be applied to at least one part of a concave of the cleaning and harvesting system of the machine. The cleaning and harvesting system includes at least one rotor and a least one concave mounted around the rotor, to which is attached and installed a removable structure that has a material retention surface, in which there are provided openings to limit grains and/or MOG passage.