Screws are a useful choice for fastening items when you need something stronger than nails or glue. Screws are also efficient choices because they can be removed without damaging the building material. An abundance of different screw types exist to serve specific purposes. When you actually go into a hardware store to select the screw you need, you should take into account the length and diameter as well as the type.
The standard wood screw is used to secure one piece of wood to another. Screws with a rounded head are generally preferred for thinner pieces of wood. Screws with a flat or oval-shaped head are a better choice when you will be countersinking the screw for a more decorative appearance.
Brass screws are essentially just wood screws that are made from brass instead of steel. They are preferable in some cases because they don't rust. Brass screws also add an aesthetic appeal that may be lost when using steel screws.
Drywall screws are very thin and straight. Threads are very deep and the point is very sharp. Drywall screws have a flat Phillips head that is technically called a Bugle head. These screws are used for securing drywall to wood or metal framing studs.
The dowel screw has threads going from near the middle to both ends. A pair of padded locking pliers is used to get a dowel screw started rather than a screwdriver. This is a very specialized screw that is used to assemble pieces of furniture, such as attaching legs to a table.
Sheet Metal Screw
Sheet metal screws can have a flat head, oval head or a pan-shaped head. The threads on a sheet metal screw go all the way down the shaft. Sheet metal screws are used to fasten a piece of thin metal to another piece of thin metal. They are good for using with wood because the deep threads provide solid stability.
A lag bolt is actually a screw that is very large and only partly threaded. The head is square and needs to be turned with a wrench rather than a screwdriver. The lag bolt is used when a standard wood screw simply isn't strong enough. It will probably be the largest screw you'll find in your local hardware store.
Security screws feature specially shaped heads that allow them to be inserted with a flat-blade screwdriver. This special shape features a slot designed in such a way that the screwdriver can grip it only when turning the screw clockwise. The security part of this screw is in the fact that since the screwdriver cannot grip it for turning counterclockwise, the screw cannot be removed.