Wood-to-wood dowel screws have wood screw threading on both ends and are used to connect two pieces of wood. A smooth section in the middle allows for use of a wrench or pliers to drive the dowel into the first piece of wood. Pre-drilled holes are needed to prevent wood from splitting. This type of fastener is most often used by hobbyists and woodworkers, particularly furniture makers. Legs on tables, shelving units and chairs are often held in place by dowel screws.