Those sharp points above the iron gate are called iron spear heads, and some are called iron dart heads, which are used to guard against theft and climb, and are called strange tricks in geomantic omen to adjust geomantic omen. Few people understand it now. All doors, whether made of wood or iron, are basically of this shape. It is used to guard against theft and prevent thieves from entering. Now, some people are looking for security, and some things are for good feng shui. In short, it is safer to have this iron thorn.