Screw (Pinyin: lu ó g ǎ n. A cylinder with a spiral groove on its outer surface or a cone with a conical spiral groove. The screw has different heads, which are called external hexagonal screws. There are also others, such as large flat screws, hexagonal socket screws, and so on. Screw Rod,Blue High Strength Studs,Standard Low Temperature Bolt,American Galvanized Full Thread Stud AM FASTENER , https://www.asmefastener.com