The fastener aisle in the hardware store houses thousands of screws, nails, bolts, hooks and more. Don't let it scare you off. It's easy once you learn a few general rules of thumb, what the numbered sizes mean and how to determine what length you'll need.
The Classic Wall Anchor
The first thing to consider is the wall type. Most newer homes have drywall. For small picture frames 8" x 10" or smaller and weighing a few ounces, a simple nail driven into the wall at a slight upward angle will do the trick. No need to worry about catching a stud. For larger and heavier frames it starts getting more complicated. Keep in mind the weight of the object as many fasteners have weight ratings. In a perfect world, a stud would be in the exact place you want to hang a picture, but we know our tastes and sightlines don't match construction techniques. Enter wall anchors. The classic wall anchor is tapped into place through a pilot hole, then a screw is driven through it. In this image, the screw causes the anchor to expand and grip the drywall with fins and expand in the back, making an anchor truly an anchor.
A wall driller is driven into the wall with a driving bit, rather than inserted into a pilot hole. It can have a screw driven through it like a classic wall anchor, or a hanger can be placed over the head of the fastener.
A third common wall fastener is a toggle bolt. Like a classic wall anchor, it is inserted into a pilot hole. What makes it unique is the spring inside, which makes the fastener pop open once it reaches the cavity behind the wall and creates a grappling-hook effect.
Time and weather take their toll, which makes your choice of fasteners for exterior projects very important. Deck screws are ubiquitous when it comes to outdoor projects. They are specially coated to resist corrosion and come in a large range of sizes, most commonly from 1 1/4" to 3". They are also considerably less expensive than stainless steel screws and aren't prone to head stripping, as stainless steel sometimes can be.
Nails or Screws?
Surprisingly, there are a wider variety of nails for exterior use than screws, whether it's for decking, fencing, siding, roofing or outdoor furniture. In this image, notice the twisted shank of a galvanized deck/fencing nail. This variety offers the increased holding strength of a screw with the value of a nail.
Deck Screws vs. Lag Screws
As their common name indicates, deck screws are clearly designed for use in deck construction, specifically for attaching deck boards, but their use extends well beyond to other projects such as outdoor furniture. For heavy-duty construction using large dimensional lumber (4x4s for example), such as deck support, pergolas, arbors, treehouses and wood swingsets, use lag screws. They come in galvanized or stainless.
Nails (and brads) are good for basic construction (building a box) and when adhesives are used. For outdoor applications, use stainless or galvanized brads or nails. Brads or finish nails are best for attaching trim and molding and for furniture assembly. They are identified by their smaller heads versus a prototypical nail. Why? The smaller heads are driven below a surface and can be concealed by wood filler.
Brad nails are very often used in pneumatic nailers and come bundled in clips rather than loose. A variety of sizes are available. For example, if a brad is labeled #18 x 1 1/4. The #18 is the thickness or gauge (the lower the number the thicker the brad). The 1 1/4 is the length in inches. In contrast, with nails, the higher the number, the thicker the nail. An example of a common size for nails would be 4d (thickness) x 1 1/2 (length).
When to Use Screws
Screws work best when forces will be applied in multiple directions such as against a joint, or if extra weight will be applied, such as a bookshelf. Use screws if you don’t plan on using additional adhesives. If you are building a simple shelf or bookcase, you can use glue and nails, but you'll feel much more secure about it if it fastened with screws. The threads of a screw grip and “bite” into the wood to make a joint stronger and more secure.
When drilling pilot holes for screws, be sure to match the diameter of the shank and not the threads. The gauge (thickness) of screws are listed similar to brads (#7, #8), but are more like nails in that the higher the gauge, the thicker the screw.
Nuts and bolts work well for projects that may need to be disassembled at some point or heavy-duty applications. They provide tremendous holding power, as you can use mechanical force (a wrench) to tighten the nut. Unlike screws, a pilot hole for a bolt should match or be slightly larger than the diameter of the threads and, of course, be drilled completely through. Bolt sizes are listed by diameter and length in inches.
What's the Correct Length to Use for a Fastener?
It depends on the application, but when joining the faces of two boards, you'll want to drive the fastener at least halfway through the adjoining board, but not completely through it. This image shows two 3/4" boards with a 1 1/4”-long screw. At that length, the screw extends into the adjoining board by 1/2" (1 1/4 – 3/4 = 1/2). Brads and screws are commonly available in 1 1/4” sizes. If joining at a right angle, use a fastener that is at least twice the thickness as the material. For example, when joining two 3/4" boards at a right angle, use a nail or screw that's at least 1 1/2” long.