Flip through a business or landlord key ring around Northwest Indiana and you will find plenty of keys stamped with three reassuring words. But do not duplicate keys carry a secret: for standard keys, that stamp is a request, not a rule — and understanding the difference matters for anyone responsible for a building.
What the Stamp Actually Means
On an ordinary key blank, DO NOT DUPLICATE is simply engraved text. There is no general law forbidding a shop from copying it, and self-service key kiosks certainly do not read it. Some counter clerks will decline out of courtesy; plenty will not. If your security plan depends on that stamp, your security plan depends on the mood of a stranger at a hardware store.
Where Do Not Duplicate Keys Give False Confidence
The risk is not the stamp itself — it is what it encourages. Owners hand out stamped keys believing copies are impossible, skip rekeying when staff leave, and lose track of how many keys exist. Years later, the lock is original, the keyholder list is unknowable, and the stamp has quietly aged into a liability.
What Actually Controls Copies: Restricted Keyways
Real key control comes from restricted or patented keyway systems. These blanks are not sold to hardware stores at all; copies can only be cut by the issuing locksmith, with authorization from the person on record. Every key can be numbered and logged, so you always know exactly how many exist and who signed for each one.
Who Should Consider It
Restricted keys shine anywhere keys pass through many hands: businesses with staff turnover, landlords, churches, clinics, storage facilities. For a single-family home, honest advice: you probably do not need them — rekeying when trust changes is simpler and cheaper.
Wondering whether restricted keys fit your building? Jacob’s Lock and Key advises businesses and landlords across Northwest Indiana, from Gary to Crown Point. Call (219) 342-5595, seven days a week, 7 AM to 11 PM.
Last updated: 08/23/2026