It is important to select the correct nail for the job at hand. The first decision to make is whether the nails should be galvanised or bright steel. If the nails were to be used in damp areas or outdoors, for example fencing, then the best type would be galvanised. The Galvanising process helps to prevent metal rusting which of course is a very important consideration when building outdoors. Bright steel, or non-galvanised nails, can be used for most other purposes.
The most common types of nail used for DIY projects are the Flat Head and Jolt Head types.
Flat Head Nails
These are good general-purpose nails and are obtainable in galvanised or bright steel. They are normally available in lengths from 20mm to 150mm. The flat head nail is a very basic type of nail and unfortunately it is liable to split wood. Because the head of the nail remains on the surface of the wood, it can make your work look ugly. The flat head nails are really only suitable for basic construction of projects where either the nail head will be covered up with other material, or the look of the finished job does not matter.
Jolt Head Nails
The head on this nail is oval and only slightly larger than the shaft of the nail itself. When it is hammered into the wood, you can use a nail punch to punch the nail home so that it sits just below the surface of the wood you are nailing. Once below the surface, the small hole that is left can be filled with wood filler or putty. As with the flat head nail, the jolt head nails are available in bright steel or galvanised steel. They range in size from 25mm to 150 mm and they are ideal for most carpentry work.
Panel Pins are small, fine gauge (thickness) nails that are used for joinery, mouldings and delicate jobs, particularly where larger nails would split the wood being worked. They are normally available in sizes ranging from 12mm to 50mm.
Tacks are short, large head nails used for fixing carpet to floors or paper and fabric to wood. They are not very decorative and therefore should only be used where they will not be seen. Sizes range from 6mm to 25mm.
These are just the very basic nails used for every day jobs. There are however many other types of nails used for specialist work. Roofing nails; Clasp nails; Clouts; Gib (Wallboard) nails; Masonry nails; Chair nails and so on. My advice is to spend a wee while at your local Mitre 10 store and familiarise yourself with the large variety of nails available. Then when you next get involved in a D.I.Y job you will know exactly the right nail to use.