Abstract: Screw fasteners are disclosed that are configured to be inserted into a variety of solid substrates, which include a bottom end that is configured to be inserted into a solid substrate and a top end that is configured to be connected to various other parts and devices. The screw fasteners include a cylindrical inner core; at least one circular flange that surrounds the cylindrical inner core; a screw thread that is helically formed around the external surface of the bottom region of the screw; and a bolt thread that is helically formed around the external surface of the top region of the screw. The pitch of the bolt thread is smaller than the pitch of the screw thread. In addition, the minor diameter and/or major diameter of the bolt thread may be greater (or smaller) than the minor diameter and/or major diameter of the screw thread.