Screws and screw rods are different from each other. Screws are generally called wood screws; It is the kind with sharp head at the front end, with large screw pitch. It is generally used to fasten wooden and plastic parts. The screw rod is a machine screw (mechanical screw), which is the flat head type at the front end. The screw pitch is small and uniform. It is generally used to fasten metal and machine parts.