Flat head has a flat top and a taper. Flat heads are designed to be used in a countersunk hole. Sheet metal screws have sharp threads that cut into a material such as sheet metal, plastic or wood. They also make excellent fasteners for attaching metal hardware to wood because the fully threaded shank provides good retention in wood. These Flat Head sheet metal screws feature a Robertson Drive, also known as a Square, or Scrulox drive which has a square shaped socket in the screw head for high torque and minimal slippage.