What is a spanner?

A spanner is a hand tool designed to grip and turn nuts, bolts, and other fasteners. In many countries, spanner is the standard term; in North America, the same tool is usually called a wrench. Spanners fit the flat sides (called flats) of a fastener’s head so you can apply torque without slipping and damaging the fastener.

How a spanner works

Spanners transfer your hand force into rotational force (torque) around a fastener. The tool’s jaws or socket match the fastener’s size and shape, spreading the load across the flats. Good fit and full contact help prevent rounding the corners of the nut or bolt.

Common DIY uses

Assembling flat-pack furniture and bed frames
Installing and removing plumbing compression fittings
Bicycle maintenance (axle nuts, pedals, headsets)
Fixing appliances and garden equipment
Mounting shelves, TV brackets, and hardware
Automotive jobs like battery terminals and brackets

Types and variations

Open-end spanner: U-shaped jaws at one or both ends. Quick to place in tight spots, but more prone to slipping on stubborn fasteners.
Ring/box-end spanner: Enclosed ring that grips all flats (often 6- or 12-point). Offers better grip and reduces rounding; great for higher torque.
Combination spanner: Open end on one side, ring end on the other, same size. A common go-to for general work.
Adjustable spanner (adjustable wrench/Crescent): Movable jaw fits many sizes. Handy for occasional use, but not as secure as a fixed-size spanner.
Socket and ratchet: A ratcheting handle drives removable sockets. Speeds up repetitive work and fits into tight areas; available in metric and SAE sizes.
Ratcheting combination spanner: Ring end has a built-in ratchet; excellent for spaces where a socket and handle won’t fit.
Flare-nut spanner (line wrench): Partially enclosed jaws for tubing nuts on plumbing and brake lines; reduces risk of rounding soft fittings.
Torque wrench: Measures and applies a specific torque setting; used where clamping force matters (e.g., automotive, machinery, some structural hardware).
Allen key/hex key and Torx drivers: Not spanners in the strict sense, but often grouped with them; fit internal hex or star-shaped fasteners.
Hook/C-spanner: Curved hook for slotted collars, locknuts, and grinder flanges.
Basin wrench: T-shaped tool for reaching up behind sinks to tighten tap/faucet nuts.
Crowfoot spanner: Open-end head that attaches to a ratchet or torque wrench for hard-to-reach fasteners.

Selecting the right spanner

Match the measurement system: Use metric spanners for metric fasteners (e.g., 10 mm) and SAE/imperial for inch sizes (e.g., 3/8"). Mixing systems leads to poor fit and rounding.
Start with a core range: For home use, a set from 8–19 mm (metric) and 1/4"–3/4" (SAE) covers most tasks. Include a 3/8"-drive socket set with deep and shallow sockets.
Choose 6-point sockets for stubborn fasteners: They grip the flats better than 12-point. Use 12-point when space or angle access is limited.
Look for quality: Chrome vanadium or similar steel, clear size markings, and tight tolerances improve grip and longevity.
Consider features: Ratcheting ring spanners, offset heads for knuckle clearance, stubby lengths for tight spaces, and flex-head ratchets add convenience.
Impact vs. chrome sockets: Use impact-rated sockets with impact drivers; chrome sockets are for hand ratchets only.

Using a spanner safely and effectively

Measure and test fit: Choose the correct size so the tool seats fully on the flats.
Prefer ring/box or socket for stuck fasteners: They offer better contact than open-end or adjustable styles.
Pull, don’t push: Pulling gives better control and reduces the chance of slipping and bashing knuckles. If you must push, use an open palm.
Keep alignment square: Keep the tool aligned with the fastener to prevent twisting off.
Break rust bonds first: Apply penetrating oil and allow time. Lightly tap the fastener head to help the oil wick in.
Use steady pressure: Avoid sudden jerks that can round corners. A longer spanner increases leverage; use carefully.
Set ratchet direction: Flip the switch for tighten/loosen. Remember righty-tighty, lefty-loosey unless the fastener is left-hand thread.
Torque critical fasteners: Use a torque wrench where specified; tighten in stages and in the correct sequence (e.g., on flange bolts).

Maintenance and care

Clean after use: Wipe off dirt and metal shavings. A light oil film prevents corrosion.
Adjustable spanners: Keep the worm gear clean and lubricated so the jaws track parallel.
Socket care: Inspect for cracks; retire any deformed sockets. Store sets on rails to keep sizes organized.
Torque wrench: Store at its lowest setting, don’t use it to loosen bolts, and calibrate periodically if used frequently.
Storage: Keep tools dry and organized; labeled trays or foam inserts help you find sizes quickly.

Common mistakes to avoid

Using the wrong size or system: A loose fit rounds fasteners. If it wiggles, try the next size down.
Over-relying on adjustable spanners: They can slip if not set snugly; use a fixed-size or ring spanner for stubborn jobs.
Cheater bars on the wrong tool: Extending a handle can break tools. Use a longer spanner or a breaker bar designed for high torque.
Open-end on soft fittings: Use a flare-nut spanner on brass or aluminum tube nuts to avoid rounding.
Using chrome sockets on impact tools: This can shatter the socket. Use impact-rated only.

Related terms

Wrench: North American term for spanner.
Socket and ratchet: Interchangeable heads and a handle that allows continuous rotation.
Torque: Rotational force applied to a fastener.
Nut, bolt, fastener: Common hardware spanners turn.
Hex key/Allen key, Torx: Tools for internal-drive fasteners.
Pipe wrench: For round pipes; different jaw design than a spanner.

Practical examples

Assembling flat-pack furniture: Most kits include a small spanner, but using your own 10 mm combination spanner speeds things up. Start fasteners by hand, snug with the open end, then finish with the ring end to avoid rounding.
Tightening a leaky compression fitting: Use two spanners—one to hold the body, one to turn the compression nut. Choose a flare-nut spanner on the nut for better grip; tighten a quarter-turn at a time and test for drips.
Bicycle axle nuts: A thin 15 mm pedal or axle spanner fits in tight clearances. Hold the wheel straight and tighten both sides evenly.
Replacing a faucet tap: A basin wrench reaches the mounting nuts behind the sink. Loosen with steady pulls, then hand-spin the nuts once free.
Freeing a stuck car battery terminal bolt: Spray penetrating oil, use a 6-point 10 mm socket on a 3/8" ratchet, and pull smoothly. Avoid twisting the terminal post.

By choosing the right style and size, keeping tools clean, and using steady technique, a spanner can make assembly, repairs, and maintenance faster, safer, and more reliable across a wide range of home projects.