A method of advancing a sausage casing mounted on a stuffing tube into a twisting mechanism includes placing a hollow natural sausage casing on the outside surface of a stuffing tube and engaging the casing with a roller. Preferably, but not exclusively, the heat sealing jaw assembly is adapted for use in a form, fill and seal machine forming thermoplastic bags. Through the above ways, on one hand the present invention can ensure the charging time of the pixel electrode and the resolution of the liquid crystal display device, on the other hand inserting the black image, achieving the inserting black image technique, reducing the 3D cross talk.