Frame lock
Also called · ring lock · wheel lock · café lock — for the quick café stop it was made for · O-lock
A lock mounted permanently on the frame that closes a steel ring through the rear wheel, stopping it from turning. Standard equipment on Dutch and many European city bikes. Most take an optional plug-in chain so the bike can also be anchored to something solid.
How to spot itA black ring or horseshoe sitting over the rear wheel, just behind the seat. On most, the key stays in the lock while you ride and only comes out once it's locked.
Best forConstant short stops. It's always on the bike, locks in one motion, and can't be forgotten at home.
Watch outIt stops the wheel turning; it doesn't attach the bike to anything. A bike locked only this way can be carried off — pair it with a lock that anchors, or add its plug-in chain.
You might say“the ring built in around the back wheel”“the lock that's part of the bike on Dutch bikes”“the black circle over the rear tire you click shut”“the one where the key stays in while you ride”
Source · AXA and ABUS frame-lock product documentation; Sheldon Brown's Bicycle Glossary (O-lock) · 2026-07
U-lock
Also called · D-lock (en-GB) · shackle lock
A rigid, U-shaped hardened-steel shackle that closes into a straight crossbar, locking the frame — and ideally a wheel — to a fixed object. The usual benchmark for everyday bike security.
How to spot itA thick, solid metal U with a removable crossbar, usually carried in a frame mount or hooked through a belt or bag strap.
Best forThe primary everyday lock: in independent ratings such as Sold Secure, U-locks give the most security for the weight and money.
Watch outIts shape is fixed. It won't close around thick posts or reach across awkward racks, so check what you'll actually be locking to before choosing a size.
You might say“the thick horseshoe-shaped one”“the solid metal U with a straight bar across the top”“looks like a giant padlock shackle”
Source · Kryptonite and ABUS product documentation; Sold Secure ratings (independent testing house) · 2026-07
Folding lock
Also called · Bordo — the original's brand name (ABUS), often used generically
A row of flat hardened-steel plates riveted end to end. It unfolds into a loop for locking and folds back into a compact block that rides in a frame holster.
How to spot itFlat steel strips with visible rivets at each joint, zigzagging open like a folding ruler; closed, it's a neat rectangular block on the frame.
Best forRiders who want more reach than a U-lock in a tidier, quieter package — it wraps shapes a rigid shackle can't.
Watch outThe rivets are the usual attack point, and folding locks tend to rate below a comparable U-lock. Check the specific model's Sold Secure rating rather than assuming.
You might say“the one that folds up like a carpenter's ruler”“flat metal strips joined by rivets that zigzag open”“folds into a little block clipped to the frame”
Source · ABUS folding-lock (Bordo) product documentation; Sold Secure ratings (independent testing house) · 2026-07
Chain lock
Also called · chain and padlock
Hardened-steel chain links inside a fabric sleeve, closed with a padlock or an integrated lock. Security scales almost directly with link thickness — and therefore with weight.
How to spot itA sleeved chain, often worn around the waist or wrapped around the seatpost between stops.
Best forWrapping thick or awkward anchors a rigid lock can't reach. The heavy versions make a strong stay-at-home lock for one fixed parking spot.
Watch outThe portable-weight versions give up much of the security; a light chain is closer to a cable than to a heavy one. Weight is the price of chain security.
You might say“the heavy chain in a fabric sleeve”“the chain people wear around their waist like a belt”“a bike chain with a padlock on it”
Source · Kryptonite, ABUS and Hiplok product documentation; Sold Secure ratings (independent testing house) · 2026-07
Cable lock
Also called · coil lock
A braided-steel cable, usually plastic-coated and coiled, with an integrated or padlock closure. The lightest and cheapest kind of lock — and the least secure.
How to spot itA springy, coiled cord that stretches out to loop around the bike, like a thick telephone cable.
Best forSecuring accessories — a helmet, a front wheel, a child seat — alongside a real lock, where its flexibility is the point.
Watch outHand cutters open most cables in seconds, and mainstream security guidance advises against using one as a primary lock. Treat it as a deterrent for opportunists, not protection.
You might say“the bendy spiral cable one”“the coiled cord lock, like an old telephone cable”“the cheap flexible one”
Source · Sold Secure guidance; San Francisco Bicycle Coalition lock guidance · 2026-07
This page names things; it doesn't sell them. Picks and prices live in the buying guides, where they're disclosed.