Using the right screw can considerably simplify the job you are doing in addition to ensuring maximum strength The choice of sizes is also important and must be carefully considered before matching to the work in hand.

Screws are usually purchased in quantity not by weight, If you are ordering screws it is necessary to give the following details gauge number, type of head, length in inches and millimetres and composition.

The length is denoted by how much of the screw actually penetrates the material being used In the case of a countersunk screw, the length is measured from the top of the head since the entire screw, including the head, penetrates the material However, with a round head screw, the length is measured from the underside of the head to the tip, as the head does not penetrate the material.

The gauge number is determined by the diameter of the plain part of the screw body Gauges 4 to 16 are the most popular.

Screws are available in a variety of finishes depending on the job they are intended to do.

When you are selecting the screw head you wish to use, consider whether you want the screws to be seen or not. The most common countersunk screw type, is used when a flush surface (as with hinges) is required.

If the screw head is exposed to moisture, select a brass screw which does not rust like steel Alternatively, a steel screw, zinc plated, will give some resistance to corrosion.

Drilling a pilot hole before inserting a screw is very important, it not only makes the insertion much easier, but makes the screw's holding power that much greater.

The first pilot hole must be nearly as long as the screw and slightly smaller in diameter to allow the screw to 'bite' into the material being used i.e. timber. The second pilot hole must be as large as the plain (unthreaded) part of the screw body and only as deep as the plain length.

The three main screw types are countersunk, round head and raised head.

Countersunk - These are the most common type of woodworking screws A pilot hole will need to be drilled as deep as the length of the screw.

Round Head - Woodworking screws that give greater fastening power A f lat washer can be placed under the head to spread the load over a wider area.

Raised Head - Often used when a more decorative effect is needed A plastic or metal screw cup can be used with raised head.