If you've ever stood in the fastener aisle — or scrolled through a product catalog — and wondered whether you need a screw or a bolt, you're not alone. The two terms get used interchangeably all the time, even by experienced tradespeople. But they're not the same thing, and using the wrong one can mean a weaker joint, a stripped hole, or a failed inspection.
At Mutual Screw & Supply, we've been answering this question since 1947. Here's the straightforward breakdown.
The Simple Definition
A screw is a fastener designed to be driven directly into a material — wood, metal, drywall, concrete — using only a screwdriver or drill. It creates its own mating thread as it goes in, and it holds by thread friction with the base material itself.
A bolt is a fastener designed to pass through a pre-drilled hole and be secured on the other side with a nut. Bolts rely on the clamping force created by tightening that nut — not on thread engagement with the base material.
The quick test: if it needs a nut to do its job, it's a bolt. If it threads directly into the material, it's a screw.
Why Does It Actually Matter?
The difference isn't just semantic — it affects load capacity, installation method, and whether a joint can be disassembled cleanly later.
Screws are ideal when:
- You're driving into wood, drywall, metal studs, or concrete
- You need a permanent or semi-permanent fastening
- There's no access to the back side of the material
- Speed of installation matters
Bolts are ideal when:
- You're fastening two pieces of material together and need maximum clamping strength
- The joint needs to be disassembled and reassembled over time
- You're working with metal-to-metal connections under high load or vibration
- Engineering specs or building codes require it
Common Types of Screws
Wood Screws — Coarse thread, tapered shank. Designed to pull two pieces of wood together tightly. The smooth upper shank keeps the top piece from "jacking" away from the bottom piece.
Machine Screws — Fine, uniform thread. Used in metal-to-metal applications, into tapped holes, or with a nut. Common in electronics, machinery, and equipment assemblies.
Sheet Metal Screws — Sharp point, coarse thread that runs the full length of the shank. Self-tapping into thin metal without a pre-tapped hole.
Self-Drilling Screws (Tek® Screws) — Tip acts as a drill bit, eliminating the need for a pilot hole. Popular in metal framing and HVAC work.
Concrete Screws (Tapcon® style) — Hardened, specially threaded to cut directly into concrete, block, or brick. No anchor required.
Drywall Screws — Bugle head, deep thread, phosphate coating. Designed specifically to sink flush into drywall without tearing the paper face.
Lag Screws — Heavy-duty hex head wood screws for structural applications. Despite the name, these are technically screws — they thread directly into wood without a nut.
Common Types of Bolts
Hex Bolts — The workhorse of the bolt world. Six-sided head, partially or fully threaded shank. Used in structural, machinery, and general assembly work with a nut and usually a washer.
Carriage Bolts — Round domed head with a square neck that locks into wood. Used in wood-to-wood and wood-to-metal connections, especially in fencing, decking, and furniture.
Flange Bolts — A hex bolt with a wide, integrated washer flange built into the underside of the head. The flange distributes clamping load across a larger surface area without requiring a separate washer, making them popular in automotive, machinery, and structural applications.
Hanger Bolts — A headless bolt with wood screw threads on one end and machine threads on the other. One end drives into wood; the other end accepts a nut to hang or mount hardware. Common in furniture assembly, overhead framing, and electrical supports.
Elevator Bolts — Feature a large, flat mushroom head and a square neck that resists spinning. Originally designed for conveyor and elevator belt systems, they're used anywhere a broad, low-profile head is needed to prevent pullthrough in softer materials like rubber, plastic, or wood.
J Bolts — Shaped like the letter J, with a hook on one end and machine threads on the other. The hooked end is cast or set into concrete foundations; the threaded end protrudes to anchor structural columns, sill plates, and equipment bases above grade.
A Note on Nuts and Washers
Bolts almost always require a nut to function, and most bolted joints benefit from a washer to distribute clamping load and protect the surface. When shopping for bolts, always spec your nuts and washers at the same grade — a Grade 8 bolt with a Grade 2 nut is only as strong as its weakest link.
The Bottom Line
When someone says "grab me a screw," they almost always mean something that drives directly into the material. When they say "bolt it together," they mean a through-fastener with a nut on the back side.
Still not sure which you need? Our team has been matching customers to the right fastener since 1947. Browse our full selection of screws and bolts at MutualScrew.com, or give us a call at 1-800-222-0324 — we'll point you to exactly what you need.
It's Better When It's Mutual.