In carpentry, the strength and stability of any structure depend largely on what’s keeping everything together. And what keep things together in carpentry are essentially called "fasteners". They are what join individual parts to form one structure or a finished product of carpentry.

The primary advantage of using wood as a structural material in carpentry is the ease with which wood structural parts can be joined together with a wide variety of fasteners such as nails, spikes, screws, bolts, pins, staples and connectors of various types. Usually they all are made of metal, and most of all of iron.

For maximum rigidity and strength, each type of fastener calls for joint designs specifically adapted to the strength properties of wood being used and to dimensional changes that could occur with changes in moisture content (that is, unavoidable weather conditions) and wear and tear.

The following are the three most popular forms of fasteners in carpentry.

Nails

Nails are the most commonly used fasteners in construction. They are the carpenter’s most useful means of fastening structural parts. As such, a great variety of types and sizes is available to meet the demands of the carpentry industry. Size is crucial in selecting the right nails for the job. Diameter would be the first consideration. Short, thick nails typically loose quickly, whereas long, thin nails are more likely to break at the joints of the lumber. Basic rule is to use as long and as thin nail as will drive easily.

Some tips in determining which nail size is appropriate:

• For lumber of medium hardness, the penny (head) of the nail should not be greater than the thickness of the board into which the nail is being driven.

• Nails should be one penny smaller if used in hard woods.

• When joining two boards together, the nail point should at least penetrate 1/4 inch of the far side of the second board.

• The kind of wood is an essential factor in determining the size of nail as well. Soft woods may require nails that may be one penny larger, or sometimes, even two pennies larger.

However, all rules and tips are worth pennies compared to experience, as it is still the best guide in determining the appropriate nail size.

Screws

Wood screws are excellent alternatives to nails as carpentry fasteners.

They have worthwhile advantages over nails because they are sturdier. Also, it gives the carpenter more flexibility in adjusting the structure because of the ease in disassembling the joined parts. Just a twist with a screwdriver and it’s off! Unlike with nails, it is quite possible to damage the structure if it’s already been nailed together and you want to take it off. These advantages, however, also come at a cost since it takes more time and effort to install screws to structural materials than nails. With nails, you just need a hammer and just pound away. Screws are more tedious because of the need for more precision.

In the early days, most wood screws (probably 75 percent or more) used to be the flat-head type. This has changed however, with the emergence of the Phillips head screw in recent years.

Bolts

An alternative to both nails and screws are called bolts. These are used to bind parts tightly together where high strength is needed. A bolt is generally regarded as a rod having a head at one end and a threaded portion on the other to receive a nut. The nut is usually considered as forming a part of the bolt.

These fasteners are as essential to carpentry as the structural materials itself. Without them to hold parts together, functionality of the structure would be greatly compromised.