Fastener names can seem like a foreign language when you stand in front of a wall of small parts. This glossary breaks them down into simple definitions, grouped by anatomy, type and drive style. Exact sizes and standards vary, so check the packaging or the maker’s guide. Beyond the definitions, it shows how to read a label, work through a choice, and avoid the mix-ups that waste time.
Anatomy of a Screw or Bolt
- Head: the top, which you turn with a driver or wrench.
- Shank: the smooth, unthreaded part under the head, on some fasteners.
- Thread: the spiral ridge that grips material.
- Pitch: the spacing between threads. Fine pitch has threads close together, coarse has them wider apart.
- Tip: the end, which may be pointed or blunt.
Types of Fastener
- Wood screw
- Has a tapered body and coarse thread meant to bite into wood.
- Machine screw
- Has a uniform thread and usually goes into a nut or a tapped hole.
- Bolt
- Usually passes through parts and is held with a nut.
- Lag screw
- A large screw with a hex head, driven with a wrench or socket.
- Anchor
- A sleeve or insert that gives a screw something to grip in masonry or hollow walls.
Drive Styles
- Slotted: a single straight groove.
- Phillips: a cross-shaped recess.
- Square: a square recess that resists slipping.
- Hex: a six-sided recess or head.
- Torx style: a six-point rounded recess.
Supporting Parts
| Part | What it does |
|---|---|
| Washer | Spreads load under a head or nut |
| Lock washer | Helps resist loosening |
| Nut | Threads onto a bolt to hold parts |
| Wing nut | Can be turned by hand |
Putting the Words to Use
Packaging often lists type, diameter, length and drive in one line. Reading it in order tells you quickly whether a fastener fits your job. For example, a label that names a wood screw, a gauge, a length and a square drive tells you what it grips, how thick it is, how deep it goes and which driver tip to bring.
- Choose the type for the material: wood, metal, masonry or hollow wall.
- Choose a diameter that suits the parts being joined.
- Choose a length that grips well without poking through the far side.
- Choose a driver that matches the recess.
When a project plan lists hardware, follow its sizes, and ask at a local shop if a name is unfamiliar.
Worked Walkthrough: Reading a Label
This label is invented to show the process. Suppose the box says: “Wood screw, 4 x 40 mm, countersunk head, square drive, coated.” Here is how to break it down.
- “Wood screw” names the type. It has a tapered body and coarse thread suited to timber, so it is not the right choice for metal or masonry.
- “4 x 40 mm” gives the diameter and the length, with 4 as a gauge or diameter number in the maker’s system and 40 mm as the length. Check the packaging or maker’s chart for how the number is defined, because systems differ between regions.
- “Countersunk head” tells you the head is designed to sit flush with, or slightly below, the surface once a recess is cut for it.
- “Square drive” means you need a driver bit with a square tip of the matching size.
- “Coated” suggests a surface finish. Look for wording about where the product is intended for use, such as indoors or outdoors, and follow the maker’s guidance.
- Compare the length with your material thickness. A common aim is for the screw to grip well into the second piece without poking out, and the packaging or project plan can confirm what is suitable.
Common Scenarios
- Shelf brackets on a plasterboard wall: screws alone may not hold in hollow material. Look for anchors the maker specifies for the wall type and the load.
- Assembling furniture with a leftover bolt: match the bolt to the nut’s thread size and pitch. Forcing a mismatch damages both parts.
- A rounded screw head: a driver that does not match the recess has spun inside it. A screw extractor or a professional may be needed.
- Outdoor use: choose fasteners the maker states are suited to exterior conditions, and avoid mixing metals where the maker warns about it.
- Replacing a lost fastener: take the old one to a hardware counter. Staff can help match thread, length and drive.
Mistakes to Avoid
- Assuming a screw and a bolt are interchangeable. A bolt usually pairs with a nut or a tapped hole, while a wood screw cuts its own path into timber.
- Mixing thread pitches. A fine nut on a coarse bolt will bind or strip, even if it seems to begin to turn.
- Using the wrong driver. A near fit looks close but can damage the head. Match tip and recess.
- Ignoring the load. Fasteners in a structural or hanging role should follow the maker’s load guidance and local rules.
- Buying by length only. Diameter, material and finish matter as much.
Quick Troubleshooting
| Symptom | Likely cause | What to try |
|---|---|---|
| Nut will not thread on | Different thread size or pitch, or damaged thread | Back off, check the sizes and clean the thread |
| Screw head strips | Wrong driver or too much force | Use the matching bit and a steadier push |
| Screw spins without tightening | Hole stripped or too large | Use a fixing made for the material, as the maker directs |
| Wood splits at the screw | No pilot hole, or screw too thick | Drill a pilot hole sized for the screw |
Care and Storage of Hardware
Store fasteners dry, because moisture rusts many types. Use small labelled containers sorted by type and then size, and keep leftover pieces from jobs in a separate tin until you identify them. Tighten caps on small tubs so contents do not spill. Discard anything bent, stripped or corroded instead of putting it back among good parts. Keep a simple note of the sizes used in furniture and fittings you own, so you can order matching replacements later.
Extra Terms Worth Knowing
- Gauge
- A number that indicates screw diameter in some sizing systems.
- Countersunk
- A head or recess shaped so the fastener sits flush with a surface.
- Pilot hole
- A small guide hole drilled before driving a screw.
- Self-tapping
- A screw designed to form its own thread in the material.
- Tapped hole
- A hole with internal threads cut for a bolt or machine screw.
- Cam-out
- When a driver slips out of the recess under load.
FAQ
How do I know which size to use?
Match the length and diameter to the materials and load, and follow the guidance from the product maker. A local shop can help match unfamiliar parts.
Can I use any driver with any screw?
No. The driver tip should match the recess. A poor match can strip the head.
What is the difference between coarse and fine thread?
Coarse thread has wider spacing and is common in wood and softer materials, while fine thread has closer spacing and is often used in metal parts. The packaging or the project plan shows which to use.
What does a washer do?
It spreads the load under a head or nut so the fastener does not sink into the material. Lock washers add resistance to loosening.
Are metric and imperial fasteners interchangeable?
Generally not. Threads differ, so check labels and maker information before mixing them.
The Short Version
Fasteners have a head, a thread and a drive style, and each type is meant for certain materials. Learn the main words, read labels in order, match your driver to the recess, and check the maker’s guidance for sizes.