This rubber cover mounts over the threshing-floor opening on the parent combine. It seals the gap between the threshing drum and the concave assembly, preventing crop material from escaping the threshing zone. A torn or missing cover allows grain loss and increases the risk of foreign material entering the cleaning system. The cover is formed from a flexible rubber sheet that conforms to the housing contour during operation. On installation, ensure the cover lies flat against the mounting surface and that all retaining hardware is tightened evenly.