The wood screw is a popular type of fastener frequently used to join pieces of wood with a strong, durable connection. Wood screws have much in common with other types of screws, as well as nails, bolts and related fasteners. The design of a wood screw is unique, though, and familiarity with its parts can help you understand how wood screws work and why they are often the best choice for woodworking or other projects.
The head of a screw is the top portion, which is usually wider than the rest of the screw and contains a slot, cross or other specially shaped opening to fit the tip of a screwdriver, wrench or drill driver bit. The head of a wood screw is usually flat, oval or round. Most wood screws are right-handed, meaning they advance by being turned, or "driven," in a clockwise direction.
The shaft of the screw is the cylinder that extends below the head and is, at least in part, surrounded by the thread. In a wood screw, the shaft generally includes a smooth (not threaded) portion (the "shank") just below the head and tapers at the bottom to a narrow point.
Wood screws typically include an area that is not threaded at the top of the shaft just below the head. This part of the shaft is called the shank.
The thread, also known as a helical ridge or external thread, is the protruding edge that wraps around the shaft of the screw. In a wood screw, the thread typically extends from the smooth portion of the shaft just below the head of the screw to the end of the shaft where it narrows to a fine point. The thread of a wood screw is designed to bore into the wood as the screw turns, lodging it firmly in place, a process known as "self-threading." With other types of screws and bolts, the screw (external) thread may be designed to interlock with the internal thread of a nut or other receptacle.
Wood screws are commonly made of plain, stainless or zinc-plated steel, but they are also widely available in brass, bronze, aluminum and other materials.