The "New Monolithic Trim Panel" does not relate to a conventional structure wherein when welding upper and lower plates, wings are formed and thereafter trim or edge tapes are manually inserted or glued, but to a structure and forming method wherein the upper iron plate is inclined bent toward the lower iron plate by an angle of 4 to 5°, thereby reducing the friction-induced noise and increasing ability of the lateral part to support a vertical load and holes for passage of injection molding material are formed in the bent part of the upper plate and the injection molding material passes through the holes of the upper iron plate during the injection molding and then is cured and thus permanently the trim is not separated..