Screw
Screw (screw) screw (wire) nail, is a common fastener, widely used in machinery, electrical appliances and buildings. General material for the metal or plastic, cylindrical, the surface engraved with the groove is called the thread. The thread is a helical slope that surrounds the side of the screw so that the screw can be screwed into a screw cap or other object, and the inside of the object has a thread corresponding to the screw, called an internal thread. General screw cap or other objects of the internal screw to be another processing, but there is a screw called self-tapping screws, you can cut in the soft objects on the internal thread, so no special processing. The main function of the screw is to engage two objects, or to fix the position of an object. Screws are usually free to remove or re-fit without compromising their efficiency, but also to provide greater strength than the nail can also be used repeatedly. ...