What are Screws ?
screw is a type of fastener, sometimes similar to a bolt (see Differentiation between bolt and screw below), typically made of metal, and characterized by a helicalridge, known as a male thread (external thread) or just thread. A screw is an inclined plane wrapped around a nail. Some screw threads are designed to mate with a complementary thread, known as a female thread (internal thread), often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together and to position objects.

There are vairous types of Screws viz :

Machine Screws Sheet Metal Screws Flat Head MS & SMS Screws Oval Head & Binding Head Screws Hex Head & Hex Washer Screws
Round Head & Pan Head Screws Truss Head & Fillister Head Screws Deck Screw Drywall Screws Thread Cutting & Rolling Screws
Phillips, Slotted & Socket Screws Six Lobe, Square & Security Screws Set Screws Socket Screws Socket Cap Screws
Slotted Flat Head Cap Screws Self Drilling Screw Particle Board Screw Wood Screw Sems Screw
Self Tapping Screw Concrete Screw Chipboard Screw Euro Screw Stainless Steel Screw
Thread Rolling Screw Roofing Screw Construction Screws Collated Screw Wing Screws
Thread Cutting Screw Coach screws Furniture Screw Cap Screws Machine screws Sheet Metal Screws
Lag Screws Binding Post Screw Multiple Material screws Wind Screws Drive Screws
Eye Screws Weld Screws Flooring Screws Dowel Screws Roofing Screws
Accordion Screws Euro Screws Jack Screws Thumb Screws Screw Hooks
Screw Eyes Security Screws