Fasteners Guide: Screws, Nails, and Bolts for DIY
Fasteners are the unsung hardware of every building project — the things holding the shelves up, keeping the deck boards flat, and making sure the cabinet doesn't slowly migrate away from the wall. This page covers the three primary mechanical fastener families (screws, nails, and bolts), how each one works at a mechanical level, which scenarios call for which type, and how to make the choice when more than one option would technically work.
Definition and scope
A mechanical fastener is any device that joins two or more materials without adhesive or heat fusion. The three types that show up in almost every DIY fasteners and hardware project are screws, nails, and bolts — and while they're often grouped together in the same bin at the hardware store, they operate on fundamentally different principles.
Screws grip by threading into material. The helical thread bites into wood, metal, or masonry and converts rotational force into clamping force that holds the joint together under tension. Nails are driven by impact and hold through friction and the elastic resistance of the surrounding material — essentially, the wood fibers spring back against the shank. Bolts pass entirely through both pieces of material and are clamped by a nut on the opposite side, creating a through-joint held entirely by the bolt's tensile strength.
That's not a subtle distinction. A 3-inch wood screw and a 3-inch nail look similar lying on a workbench. Under lateral load, the screw resists withdrawal far more effectively. Under shear load applied perpendicular to the shank, a nail can outperform a screw of equivalent diameter because nails are typically made from more ductile steel that bends rather than snaps.
How it works
Each fastener type has a specific load path — meaning the direction in which it's designed to resist force.
-
Screws (tension/withdrawal resistance): The thread profile determines how much holding power a screw develops. A coarse thread in softwood creates more contact area per inch of penetration than a fine thread. The International Residential Code (IRC), published by the International Code Council (ICC), specifies minimum fastener schedules for structural applications like deck ledger connections and shear wall sheathing — these are not suggestions.
-
Nails (shear resistance and speed): Common wire nails, box nails, and ring-shank nails each behave differently. Ring-shank nails — those with annular ridges along the shank — provide withdrawal resistance approaching that of screws, which is why building codes in hurricane zones frequently require them for roof sheathing. The difference between a smooth-shank and ring-shank nail in withdrawal resistance can exceed 40 percent (USDA Forest Products Laboratory, Wood Handbook).
-
Bolts (structural through-connections): Bolts are measured by diameter, thread pitch, length, and grade. A Grade 5 bolt (3 lines on the head) has a minimum tensile strength of 120,000 psi; a Grade 8 bolt (6 lines) reaches 150,000 psi, per standards maintained by the Society of Automotive Engineers (SAE) and referenced in structural applications. For most DIY deck or pergola hardware, carriage bolts — with a domed head and square shank that self-locks against the wood — are the standard choice.
Common scenarios
The same project can require all three fastener types, which is part of what makes fastener selection feel more complicated than it is.
- Deck framing: Joist hangers use short, thick structural screws or joist hanger nails (not drywall screws — drywall screws are brittle and fail the snap test in structural shear). Ledger-to-house connections require lag screws or through-bolts sized to the IRC's Table R507.9.1.3 fastener schedule.
- Cabinet installation: Screws driven into wall studs. For frameless cabinets spanning stud bays, toggle bolts rated to the actual load — most hollow-wall toggle anchors are rated between 50 and 200 lbs depending on wall material and toggle size.
- Subfloor repairs: Ring-shank nails or coarse-thread screws both work; screws eliminate squeaking more reliably because they don't back out as the wood cycles through humidity changes.
- Concrete anchors: This is technically a bolt variant — a sleeve anchor, wedge anchor, or Tapcon screw — but the selection logic follows the same load-path reasoning. The American Concrete Institute (ACI) publishes anchor design standards in ACI 318, which specifies minimum edge distances and embedment depths.
For a broader view of how materials choices interlock with fastener selection, the DIY materials guide provides context on substrate properties that directly affect which fastener performs.
Decision boundaries
When more than one fastener type would technically work, the decision narrows to four criteria:
Load direction — Tension parallel to the shank favors screws. Shear perpendicular to the shank favors nails or bolts. Through-connections with reversible load favor bolts.
Material — Hardwoods like oak and maple require pre-drilling for screws (splitting risk is real above 3/16-inch shank diameter). Pressure-treated lumber requires corrosion-resistant fasteners — hot-dipped galvanized, stainless steel, or specifically approved coated fasteners — because the copper compounds in modern ACQ-treated wood corrode plain zinc-plated steel. This is an explicit code requirement, not optional.
Removability — Bolts win here. A bolt with a nut can be disassembled cleanly. A screw can be backed out. A nail is a commitment.
Speed — On a roofing job, a pneumatic framing nailer drives 3-inch nails faster than any screw gun. For a single repair or precise joinery, a screw's control advantage outweighs the time difference.
The home improvement DIY reference covers broader project planning context, and the site index maps all reference pages across the full DIY topic library, which is useful when a project crosses into multiple disciplines — say, a bathroom remodel where framing, tile substrate, and fixture mounting each call for a different fastener logic.