Why Your Copied Key Doesn't Work, and What "Do Not Duplicate" Actually Means

A copied key that sticks, won't turn, or works in one lock and not another is almost never a bad lock. It's a bad copy. Every time a key is cut from another key instead of from the lock's own specifications, a small amount of accuracy is lost, and that loss compounds the more generations away from the original the copy sits. A key stamped "Do Not Duplicate" adds a separate question on top of that: most of the time, that stamp is a request, not a lock.

This is common in Calgary homes and rentals, where keys get copied at a hardware store or a kiosk for years without anyone cutting a fresh one from the original. Below is why copies drift, what actually separates a duplicated key from one cut to code, and what "Do Not Duplicate" does and doesn't do.

Why Does a Copied Key Stop Working After a While?

A copied key drifts because each copy is cut from the copy before it, not from the lock. Every cutting pass introduces a small margin of error, so errors stack across generations rather than resetting each time. A key that was a third or fourth generation copy can be visibly worn along its cuts even though it looks fine to the eye.

Four things drive this, and they usually combine:

• Copying a copy. If the key handed over the counter was itself a duplicate, its cuts are already slightly off from the true depths cut into the lock's pins. The new copy inherits that error and adds its own.
• Blank quality. Cheaper blanks are softer metal and wear at the cutting edges faster, especially once they've been through a few winters of grit and road salt in a coat pocket.
• Machine calibration. A duplicating machine that hasn't been checked or calibrated recently cuts slightly shallow or slightly deep across every key it produces that day, not just one. High-volume kiosks and self-serve machines are the ones most likely to drift out of calibration between checks.
• A worn original. If the key being copied has itself worn down from years of use, the copy faithfully reproduces that wear rather than the lock's true specification.

The result is a key that turns hard, needs to be jiggled, or works in the front door but not the side door on locks that were supposed to be keyed alike. None of that means the lock is failing. It means the key stopped matching the lock's actual pin stack.

What's the Difference Between a Duplicated Key and One Cut to Code?

A duplicated key is copied from another key. A key cut to code is cut from the lock's own specification, either read directly from the lock's pins or pulled from a recorded key code, and it matches the lock rather than matching another key. This is the more accurate method because it removes the compounding error a duplicate carries forward.

Cutting to code means the locksmith either decodes the lock itself (reading the actual pin depths with the right tools) or works from a code recorded at the time the lock or key set was made. Either way, the new key is built against the lock's true specification, not against whatever cuts happened to be on the key someone handed over. That's why a key cut to code from a lock that's been giving trouble will often turn smoothly again, where copying the worn key that opened it would have carried the same problem forward.

For a rental or a home changing hands, this distinction matters more than it looks like it should. A landlord or new homeowner who copies the outgoing tenant's or seller's key duplicates whatever wear and drift that key already had. Cutting a fresh key to code, or rekeying the lock outright, starts clean instead. See the guide on rekeying versus replacing locks in Calgary for how to decide between the two.

What Does a "Do Not Duplicate" Stamp Actually Mean?

A "Do Not Duplicate" stamp is a request printed on the key, not a technical or legal lock on copying it. In most circumstances, it does not stop a hardware store, a locksmith, or a self-serve kiosk from cutting a copy if they're willing to. The stamp relies entirely on the operator choosing to honour it.

This surprises a lot of people, because the stamp looks official. It isn't a restricted keyway, a patented blank, or a registered key system. It's a standard key blank with four words stamped into the bow, and any shop with a compatible blank on the wall can cut it the same as any other key. Some retailers have an internal policy to refuse a key stamped that way. Many don't check at all, especially at unattended kiosks.

The stamp is a courtesy marker, not a control. If the goal is to actually restrict who can get a copy made, a "Do Not Duplicate" stamp on an ordinary key blank doesn't achieve that on its own. Read on for what does.

Is It Illegal to Copy a Key Stamped "Do Not Duplicate"?

This isn't a legal question this article can answer, and it varies by situation, so treat this as general information rather than legal advice. What can be said plainly: in most everyday circumstances, a locksmith or retailer cutting a key stamped "Do Not Duplicate" isn't automatically breaking a law by doing it. The stamp itself doesn't create a blanket legal restriction the way a genuinely restricted keyway does.

Where it gets more complicated is context. A landlord who copies a tenant's stamped key without authorization, or someone copying a key they don't have a legitimate right to hold, can run into other legal issues that have nothing to do with the stamp itself, like unauthorized access or a lease violation. The stamp doesn't create those problems and it doesn't prevent them either; it's the underlying circumstances that do. If there's a real dispute over who's allowed to have a key copied, that's worth raising with a lawyer, not settling off a four-word stamp.

What Is a Genuinely Restricted Key, and How Is It Different?

A genuinely restricted key uses a patented keyway that ordinary blanks physically cannot fit, so copying requires proof of authorization from a locksmith who carries that specific system. This is the real version of what people assume "Do Not Duplicate" does on its own. The restriction lives in the shape of the key and the blank supply chain, not in a stamp.

With a true restricted system, a code card or signed authorization is usually required before a locksmith will cut a copy, and the blanks themselves aren't sold over the counter at hardware stores or kiosks because they physically don't match anything on the standard wall rack. That's the mechanical difference between a system that actually controls duplication and a stamp that only asks for cooperation. Restricted systems are common in commercial buildings, condos, and multi-unit properties where a property manager needs a real handle on who can get keys cut.

For a single-family home, a full restricted system is usually more than the situation calls for. Where it does come up for homeowners is after a life change, a lost key, or simply wanting to know exactly how many working copies exist. The guide on rekeying a Calgary home after a breakup covers a common version of that decision. Landlords managing turnover between tenants face a similar version of the same question, covered in the guide to rekeying between tenants.

Why Do Hardware Store and Kiosk Copies Drift More Than a Locksmith Cut?

High-volume, self-serve key copying is built for speed and low cost, not precision, so the drift described earlier shows up more often from that route than from a locksmith cutting a key by hand or decoding it directly from the lock. That's a description of the category and how it operates, not a claim about any specific retailer or brand.

Self-serve and automated machines run high volumes with minimal manual checking between keys, and the blanks stocked at that price point are usually the cheapest ones available rather than the ones best matched to a given lock brand. A locksmith working by hand can feel resistance while cutting, catch a blank that's the wrong depth spec for that lock, and decode directly from the lock itself when a key isn't available to copy at all. None of that is available from an unattended machine.

This doesn't mean every hardware store copy fails. Plenty work fine for years. It means the odds of a clean, accurate copy go down as the process gets faster and less supervised, and a key that already turns hard is a common early sign the copy on hand has drifted rather than the lock failing.

What Does a Proper Key Cut Cost in Calgary?

A standard house key cut in Calgary typically runs in the same $15 to $25 range published in this site's 2026 locksmith price guide. A key cut to code, decoded directly from the lock rather than copied from another key, generally costs more because it takes longer and may involve inspecting the lock first, typically landing in the same $50 to $100 range that guide lists for more involved cutting and lock work.

These figures come from the range already published on this site rather than a fresh quote, and the exact price for any given job depends on the lock brand, how many keys are needed, and whether the lock needs to be inspected or opened to decode it. A locksmith can usually give a firm number once they've seen the lock or the existing key.

Car keys, transponder keys, and fobs follow a separate and often higher pricing structure tied to the vehicle's electronics, not the mechanical cutting discussed here. For that side of the picture, see the car key replacement cost guide.

What Should You Do If Your Copied Key Won't Turn?

Stop forcing it. Forcing a key that won't turn smoothly risks snapping it off inside the cylinder, which turns a simple key problem into a lockout. The safer move is to try the original key if one still exists, and if the original also struggles, the lock itself may be worn rather than any particular key.

If no original is available or the original has the same problem, the accurate fix is a key cut to code from the lock rather than another copy of the same worn key. That resets the accuracy instead of carrying the same drift forward again. A locksmith can also tell quickly whether the issue is the key, the lock's pins wearing out, or something environmental like frost affecting a door lock in winter.

Get a Key Cut Right the First Time

A key that's been copied from a copy from a copy is often the quiet cause of a lock that "just needs jiggling." Cutting a fresh key to code from the lock itself, rather than duplicating whatever's on hand, is the straightforward fix, and it costs little more than an ordinary copy in most cases.

Key And Lock Solutions is a family owned and operated locksmith serving Calgary and the surrounding areas, working on residential locks and keys across the city. No shortcuts, no unnecessary upsells, doing the job right the first time. If a key has stopped turning cleanly or it's time to know exactly what's been copied and by whom, get in touch and a cut can be sorted from the lock itself rather than another worn copy.