Nails are the most common metal fasteners used to connect pieces of wood in construction. Originally, nails were hand made by a blacksmith and were rare and expensive, so builders would often remove them from one structure for use in later ones. Today, you have several types of framing nails to choose from. Different nails work better than others for roofing, flooring, and other construction.
Common
The most frequently used type of framing nail is called a common nail. These are used for framing and also general fastening needs. They have a flat head and a barbed shaft, which gives them good holding power. Some common nails have textured heads to keep the hammer from slipping as you pound them into place.
Duplex
Duplex nails are mainly used for temporary construction, scaffolding and theatrical scenery. These nails have two heads that are separated by about one-quarter of an inch. The nail is driven into the wood up to the first head. When it is time to remove it, you can use a claw hammer to grab the second head and pull it out.
Spiral
Spiral nails are popular because of their strong bonding power and because they don't squeak. They have a spiraling line down the shaft that is similar to screw threads. These nails are popular for building rafters, attaching wood or vinyl siding, or securing hardwood flooring to the sub floor.
Ring Shank
Ring shank nails have great holding power because of a series of concentric rings along the shaft. These nails work to split the wood and then allow the fibers to settle into the spaces between the rings, forming a strong bond. Ring shanks are used primarily with drywall, sub floors and plywood. They are difficult to remove without damaging the nail and the wood.
Roofing
Roofing nails hold shingles and roofing felt in place. These nails have large flat heads and are often chemically treated to prevent rust. Their shaft is usually lightly ringed to help form a stronger bond with the wood frame, and sometimes have rubber, plastic or metal washers attached to help prevent leaks.