Finish nails are nails with very small heads, not much bigger than the body of the nail, they are made from steel wire of various thicknesses which are referred to as gauges. They range in size from 1 to seven inches. The gauge sizes increase as follows, a 12d nail is 3.5 inch long, and the sizes increase by 1/4 inch increments until it reaches 16d. At that point, the length increases in 1/2-inch increments. They are available in 2d to 20 d thicknesses. The gauge of nail, or the thickness of the shaft, will increase in relation to the length of the nail. The smaller the gauge the harder the nail. The heads tend to have a slight indentation so that the head can be driven slightly below the surface, this is to ensure that the nails are not visible. There are several different types of finishing nails including common nails brads and castings. Brads are essentially a thinner gauge of nail used to attach lightweight trim. They are normally made of steel but can be made from stainless steel, iron copper aluminum or bronze.
Finishing nails as the name suggests are used to finish off a job on your home, that you want to look neat and tidy and thus want the nails to be almost invisible. They are usually used for final touches so that the nail does not look like a prominent feature of the area they are holding together. Thus, these nails are not intended for heavy duty use or weight bearing areas rather they are used for interior doors or, for counter top trims or wainscoting. Possibly the most common use of finishing nails is in moulding and trim around the interior of a home. For this reason, it is also possible to get these nails in colors that will match the trim of your new work area. They are used by allowing a nail set to countersink the nail into the chosen area. A nail set is a pointed piece of metal that is placed against the head of the nail and then a hammer is used to drive it so that the nail is flush or even slightly indented to the surface of the area where it is being used. This is so that the indentation can be filled with putty or other filler and sanded so that the nail is not visible and so that the job looks very neat and tidy.
The length of your nail is determined by the area that you want it to cover and also that you want it to remain inconspicuous. For example, if the width of the wood is half an inch then the nail should be three times the size at one and a half inches. The rule is therefore that the nail should be three times longer than the width of the wood. As these nails are used in finishing work it is not likely that they will be call for nails longer than five or six inches at a maximum.