Are you feeding cat food, or hog food. Some rats aren’t so keen on cat food, so that might help – if you don’t have a cat problem as well! Otherwise, check the area for bolt holes made by the rat and fill them in. I usually pour water down first, to make sure no-one’s there. I wouldn’t want to bury one, by mistake! But they do like to have a bolt hole, so it’s just another deterrant. Also, if you feed the birds, make sure there isn’t any bird food lying around.