MidWest Homes for Pets 183 Ferret Nation Add-On Unit Unique Features. Removable, Plastic Less Mess Shelf pan can easily be lifted off for cleaning. Reversible, Washable, “Happy Feet” Ramp Cover is included. It slips easily, but securely, over the ramp. Be sure to slip on each cover starting from the bottom of the ramp so the ramp hooks are exposed at the top.