The expansion of the lines means that the visible surface of the irregular lines is straightened; the hemming of the stone is a small edge added to the side of the flat stone (usually a shape with an inside-out relationship, which is directly glued to the side of the stone) One edge); the stone of the grille bottom window must be folded into three sides. This must mean that the stone under the window has a corner. The folding mentioned here is the corner of the stone; the back cover of the bay window refers to the edge closing (closing). How to close it depends on the drawing; the cover plate. A better understanding is that the facade stone needs a flat stone to cover it on the top, which is the cover;... These terms are not professional terms. If you understand, you can also name the stone cover yourself. It’s called capping stone