The screw thread on the screw is a special rib for wood screw, which can be directly screwed into the wood components(or parts).
Detailed Information
Wood screws are widely available in all home centers and hardware stores and are designed to join two pieces of wood together. They are threaded part of the way and then have a smooth shank at the top. This helps hold the screws in place. They are relatively inexpensive and come an all kinds of diameters and head shapes.