Why the choice of fastener matters
A fastener does two jobs. It keeps parts from pulling apart, and it keeps them from sliding past each other. Different fasteners are good at different parts of that, and most failures come from using a fastener for a job it was not designed to do. Knowing the main fastener types makes it much easier to read a package label or a set of plans and understand why a particular piece of hardware was specified.
This overview covers the main families. The other articles in this section go deeper on individual topics.
Two kinds of load
Two terms come up constantly.
Withdrawal is a pull along the length of the fastener, trying to yank it straight out. A shelf hanging from a screw in a ceiling puts the screw in withdrawal.
Shear is a force across the fastener, trying to cut or bend it. A shelf bracket screwed to a wall carries the shelf’s weight mostly in shear.
Most fasteners resist one kind of load better than the other. A nail, for example, usually performs better in shear than in withdrawal. Whenever you can, arrange a joint so the fasteners are loaded in the direction they handle best.
Nails
Nails hold by friction. The wood fibers squeeze against the shaft, and ridges, rings or a coating can increase that grip. Nails are fast to drive, inexpensive and slightly flexible, which is a real advantage in framing, where a little give is better than a brittle failure.
Their weakness is withdrawal. Wood moves as it takes on and loses moisture, and a smooth nail can slowly work loose. Nails are well suited to framing, sheathing, trim and general carpentry, where the load is mostly shear and speed matters. A hammer does the job by hand, and a pneumatic nailer drives them far faster in production work. Choosing the right length and diameter is its own subject, covered in the article on nail sizes.
Screws
A screw holds by thread engagement. The thread cuts into the material and pulls the two parts together, so a screw can clamp a joint tight and resist withdrawal much better than a nail of similar size. It can also be backed out and reused, which makes screws the usual choice for anything you may need to take apart or adjust.
The trade-offs are speed and brittleness. Driving screws takes longer, and many screws are harder and more brittle than nails, so they may snap under sharp sideways impact. Different screws are made for different materials: wood screws, drywall screws, machine screws, self-tapping screws for sheet metal, and concrete screws for masonry. Using a drywall screw where a structural screw is called for is a common mistake. Screws are normally paired with the right drill bit and driver, and an impact driver is popular for driving long screws without strain on the wrist.
Bolts, nuts and washers
A bolt passes through both parts and is tightened with a nut on the far side. Because the clamping force comes from the nut and the bolt’s stretch rather than from threads biting into wood or metal, bolted joints can be very strong and are easy to take apart again. They are the standard answer for heavy timber connections, machinery, vehicles and anywhere strength matters more than speed.
Washers spread the clamping force over a larger area so the nut or head does not crush the surface. Bolts come in different strength grades and thread pitches, which is why mixing parts needs care. Checking that a nut matches the bolt’s thread is a basic habit, and the topic of thread pitch comes up often in automotive work.
Rivets, staples and other options
Pop rivets join thin sheet metal quickly when access is available from only one side, though they are not meant for structural loads or for joints that must be disassembled. Staples are used for upholstery, wire fencing and light sheathing. Adhesives are often used together with fasteners, particularly in woodworking, where glue carries much of the load and screws act as clamps until it cures.
Anchors for hollow and masonry surfaces
Wood and metal take screws directly, but drywall, brick and concrete usually do not. Anchors expand or grip inside the wall so a screw has something solid to hold. The right choice depends on the wall type and on whether the load pulls straight out or hangs down. Where possible, fasten into a framing member located with a stud finder rather than relying on an anchor in a hollow wall.
Matching the fastener to the job
A few questions narrow the choice quickly:
- What is being joined? Soft wood, hardwood, sheet metal, drywall, masonry and treated lumber each have preferred fasteners.
- Which way is the load? Mostly sideways favors nails or bolts. Mostly pulling out favors screws and bolts.
- Will it ever come apart? If yes, use screws or bolts.
- Where will it live? Outdoor and damp locations call for corrosion-resistant hardware, because ordinary steel will rust and stain.
- How much does failure matter? Hanging a picture is not the same as supporting a deck or a ladder. For anything structural or where people could be hurt, follow the plans, local building codes and the manufacturer’s load information, and ask a qualified professional if you are unsure.
Safe working habits
Wear eye protection when driving nails, since fasteners and chips can fly, and use hearing protection with pneumatic or other loud tools. Check for hidden wires and pipes before driving fasteners into walls. Unplug a corded tool or remove the battery before changing bits. Buy fasteners in boxes with clear labels rather than loose and unmarked, so you can confirm size and material later.
This is general information and not professional trade advice. Building codes and product ratings vary, so always read the instructions that come with the hardware.