Common Fasteners Explained: Screws, Bolts, Anchors, and When to Use Each

Screws: The Everyday Workhorse

Screws are threaded fasteners designed to be driven into a material — typically wood, drywall, or metal — using a screwdriver or drill. Their helical threads grip the surrounding material, creating a pull-down force that holds two surfaces together without a nut.

Common Screw Types

• Wood screws: Coarse threads with a tapered shank. Best for joining solid wood or plywood. The partially unthreaded shank lets the top board pull flush against the bottom piece.
• Drywall screws: Fine or coarse threads with a bugle head that countersinks cleanly. Designed specifically for attaching drywall to wood or metal studs — not ideal as a general-purpose fastener.
• Sheet metal screws: Fully threaded from tip to head. Cuts its own thread as it drives into thin metal, making it useful for HVAC ducts and metal brackets.
• Deck screws: Coated for outdoor moisture resistance, with serrated threads that resist the wood's natural expansion and contraction.

Drive type matters too. Phillips, square (Robertson), and Torx heads each have tradeoffs in cam-out resistance and tool availability. Always match your bit to the head recess to avoid stripping.

Bolts, Nuts, and Washers: When You Need Real Holding Power

Unlike screws, bolts pass entirely through a material and are secured on the far side with a nut. This through-connection distributes load more evenly and is the right choice when a joint will face significant shear or tension forces — think deck ledger boards, structural brackets, or heavy machinery mounts.

Common Bolt Types

• Hex bolts: The standard six-sided head bolt used in framing, machinery, and metal fabrication. Available in a wide range of diameters (typically ¼" to 1") and grades.
• Carriage bolts: A domed, smooth head with a square shoulder beneath it. The square locks into wood as the nut tightens, preventing spinning — ideal for wood-to-wood structural connections.
• Lag bolts (lag screws): Heavy-duty fasteners with a hex head and coarse wood-screw threads. Driven directly into wood without a nut, they're used for structural connections such as attaching a ledger board to a house rim joist.

Washers Matter

Flat washers spread the clamping load over a larger surface area, protecting softer materials from the head or nut digging in. Lock washers and nylon-insert locknuts resist loosening under vibration. Never skip washers on structural or load-bearing connections.

For detailed context on tackling structural connections and other first repairs, see our complete DIY home repair guide.

Wall Anchors: Fastening Into Hollow or Weak Surfaces

When there's no stud, joist, or solid backing to drive into, a wall anchor transfers the load to a wider area of the wall surface itself. Choosing the wrong anchor — or skipping one entirely — is a leading cause of mounted shelves, mirrors, and fixtures failing unexpectedly.

Anchor Types by Surface

• Plastic expansion anchors: The small ribbed plugs included with many hardware kits. Suitable only for light loads (picture hooks, small shelves) in drywall or masonry. They expand as the screw is driven in.
• Threaded drywall anchors (E-Z Anchors): Self-drilling anchors with coarse outer threads that bite into drywall without a pilot hole. Rated for moderate loads — typically up to 50 lbs. in ½" drywall, though always verify the manufacturer's rating.
• Toggle bolts (butterfly toggles): A bolt with spring-loaded wings that open behind the wall. These provide strong holding power in hollow walls — often 100 lbs. or more for heavy items like TV mounts. Requires a larger pilot hole.
• Snap toggles (strap toggles): A reusable channel-and-bolt system. The plastic strap keeps the toggle in place even if you remove the bolt, making them useful for items you need to take on and off.
• Masonry anchors (wedge anchors, sleeve anchors): For concrete or brick walls. Require a hammer drill and masonry bit. Used for mounting heavy shelving, water heaters, or structural brackets in basements and garages.

Always check the anchor's rated load against what you plan to hang — and when in doubt, find the stud.

Matching Fastener to Task: A Quick Decision Guide

Choosing correctly comes down to three questions: What material am I fastening into? How much load will this joint carry? Will it be exposed to moisture or movement?

When a project involves structural connections, electrical boxes, or load-bearing elements, verifying local building code requirements and consulting a licensed contractor is always the prudent step. Understanding fastener vocabulary also helps when reading design plans — if you want to brush up on broader home terminology, our home décor glossary is a useful companion reference.