This invention provides a method of making a fluorinated precursor of a superconducting ceramic. A restricted opening is formed by at least partial detachment of a dispensing flap, which permits limited access and side dispensing. It is attractive, lightweight, durable, inexpensive to manufacture and easy to install. In the front part of the third covering part, a plurality of through holes are provided. Once the glass panel is in place, a vacuum sucks the panel against the stage, holding the panel tightly against the stage.