Pennsylvania Statutes Title 53 P.S. Municipal and Quasi-Municipal Corporations § 24945. Openings through proscenium wall

There shall be no opening through the proscenium wall, except the curtain opening, and not more than two others, which shall be located at or below the level of the stage.  These latter openings shall not exceed twenty-one superficial feet each, which shall have doors of iron or wood in each face of the wall, and, if of wood, the door shall be lined with tin and securely hung to rabbeted iron frames or rabbets in the brick wall.  They shall be hung so as to be opened from either side at all times.  Direct access to these doors shall be provided on both sides, and the same shall always be kept free from any incumbrance.