Abstract: A method and apparatus for forming a plastic film-protected external siding board in a molding press having an upper normally closed heating box open at its lower end, and a support system below the upper box which supports a board core with a plastic film disposed over it to project beyond its side and end edges. The upper box and film are brought into engagement to close the heating chamber with the film which is then billowed upwardly in the heating chamber to prevent it from sagging while heat is applied to raise the film to molding temperature. A differential pressure is then applied to the film to mold it to the core.