All transparent glass doors and fixed adjacent transparent glass sidelights shall be marked as hereinafter required, regardless of the type of glazing material used in their construction. Marking of all transparent glass doors and fixed adjacent transparent glass sidelights within six feet horizontally shall be of an opaque nature placed as hereinafter described in section 47.8 below and shall be of such a design as to be readily discernible to any person approaching the doors and sidelights from any direction.