Commercial & property management

Do Not Duplicate keys: what the stamp really does, and what works

Building owners love the DO NOT DUPLICATE stamp, and tenants know it is mostly decoration. If copies of your keys actually matter, the answer is in the keyway, not the stamp.

By Timmy Creighton, founder and licensed locksmith · Major Key Locksmith · October 2026

What the stamp does

It asks a key cutter not to copy the key. Some will refuse. Plenty will not, and self-serve kiosks may not notice at all. The stamp is a courtesy, not a control.

What actually controls copies

A restricted keyway. The key blank has a profile that is not sold to hardware stores, so ordinary key cutters cannot get blanks for it.
A patented keyway. The same idea with legal protection behind it. Blanks are available only through authorized locksmiths, and copies are cut only for the registered owner or someone they authorize.
A key register. A record of every key issued, by number, to whom and when. When keys can only come from one place, the register is actually true.

Cut on site, not sent out

Sending a building’s keys out to be copied means they leave your control for a day. We cut keys at the property instead, so nothing leaves. It is $5 per standard key with a minimum order of 50 keys, plus the mobile service charge once for the visit. Restricted and high-security keys are priced separately.

Where to start

For most buildings: put the common doors, where copies hurt most, on a restricted or patented keyway first, keep a register, and fold it into a master key system so management carries one key.

Questions people ask

Is it illegal to copy a DO NOT DUPLICATE key?

The stamp on its own is generally a request rather than a legal barrier. Patented keyways are different, because the blanks themselves are controlled.

Can tenants still get copies of a restricted key?

Only through the authorized locksmith, and only with the owner’s authorization. That is the point.

Do we have to replace all our locks to get key control?

Not usually. The cylinders change, and the rest of the hardware often stays.

Want a straight answer about your building?

Tell us what you are dealing with. We will say what it needs, what it costs, and whether it is a job for us at all.

On-site key duplication Call 973-922-3597

Keep reading

What actually makes a lock high-security? Picking, bumping and key control. Why the key you cannot copy is the real feature.Read → Master key systems explained for building owners and managers Grand masters, masters and change keys in plain English, plus the trade-off nobody mentions.Read → A locksmith’s unit turnover checklist for property managers Every unit lock, the mailbox, codes and fobs, and the key log that makes the next one faster.Read → How many keys to your house are already out there? Previous owners, contractors, cleaners, the realtor lockbox. You will never get an honest count.Read →

Any price mentioned here is the one published on our pricing page as of October 2026. The final price is always confirmed with you before any work begins. More answers from the blog →