Smart locks are sold on convenience — PIN codes, fingerprints, RFID cards, app unlocks, and remote access via Wi-Fi. But there’s one feature that regularly catches people out because it behaves like an old-school mechanical lock feature, not a smart function:

Secure Lock (also called the internal snib or privacy snib).

This guide explains what Secure Lock is, what it completely disables, what it does not disable, and why misunderstanding it is one of the easiest ways to create an unexpected lockout — especially at a rental property. It covers:

• What Secure Lock actually does at the hardware level
• Every credential type it blocks
• Why the mechanical key still works
• Why admin app override does not work
• How to tell if it’s currently engaged
• The specific risk for Airbnb and short-stay rental hosts

If your lock has suddenly stopped accepting all credentials, Secure Lock is the first thing to rule out. See also: Smart Lock Not Locking? 3 Common DIY Mistakes.

This guide was reviewed and updated in May 2026.

What Is Secure Lock (Internal Snib)?

Secure Lock is a physical privacy function activated from the inside of the door. It is designed to prevent people outside from gaining entry using any smart credential.

Think of it as a “do not disturb” mode for your front door — except it is implemented at the lock hardware level, not in software. When you turn the snib to the locked position, the lock’s credential-reading electronics are physically isolated from the latch mechanism.

Not every smart lock has a physical snib. Simpler models may have no privacy function at all. If your lock has a small dial, lever, or button on the interior face near the handle, that is almost certainly the Secure Lock mechanism. For a full breakdown of access method behaviour on different lock types, see Chapter 03 — Smart Lock Access Methods.

What Secure Lock Disables

When Secure Lock is engaged, it locks out every digital access method without exception:

• PIN codes (all users, all code types)
• Fingerprint access
• RFID cards and fobs
• Bluetooth eKey unlocks
• App unlock commands (local Bluetooth)
• Remote unlocks via Wi-Fi bridge or gateway
• Voice assistant commands

Simple rule: If it is a digital credential, Secure Lock will block it — including credentials held by an administrator or property owner.

What Secure Lock Does Not Disable

Secure Lock does NOT lock out the mechanical override key. If the lock has a key cylinder and someone has a correctly cut mechanical key, that key can still unlock the door even when Secure Lock is fully engaged.

This is intentional. Mechanical keys remain the ultimate backup access method for flat batteries, phone issues, Wi-Fi dropouts, and emergencies. The hardware snib cannot physically prevent a key from turning the cylinder — these are two entirely separate mechanisms within the lock body.

Security implication: People often assume Secure Lock means “nobody gets in.” That is not accurate if mechanical keys have been issued and are in circulation. Secure Lock blocks smart credentials — not a physical key held by someone else.

Can the Admin Override Secure Lock in the App?

This is the most common question: “If someone turns on Secure Lock from inside, can the admin just override it in the app?”

In practice, no. And the reason is important to understand.

Why app override doesn’t work: Secure Lock is not a software setting — it is a physical hardware state. When the snib is turned, it mechanically isolates the credential-reading electronics from the latch mechanism inside the lock body. The lock’s processor receives the unlock command from the app, but the physical hardware block prevents it from executing. There is no software permission level that can override a hardware isolation — not even administrator access.

Admins can manage users: add or remove PINs, issue or revoke eKeys, view logs. But if Secure Lock has been physically engaged at the lock, those credentials will be refused until someone physically disengages the snib from inside the door. The lock treats the snib as local-hardware priority — the physical action takes precedence over all app commands.

How to Tell If Secure Lock Is Engaged

Secure Lock can only be checked and disengaged from inside the door. There is no way to determine its status or change it from outside — which is exactly the problem when a lockout occurs.

The red box highlights the internal snib in the locked (Secure Lock) position. On this lock, the snib is a small rotary dial on the interior face. When turned to the locked indicator, all digital credentials are blocked until it is rotated back.

Indicators that Secure Lock is engaged:

• Visual: The snib dial or lever is visibly turned to the locked position — often marked with a padlock icon or the word LOCK. Compare to the unlocked position to confirm.
• App indicator: Some lock models display a Secure Lock status in the app when connected via Bluetooth or gateway — look for a lock-within-a-lock icon or "Secure" label.
• LED or audio: Some models beep or flash differently when an unlock is attempted while Secure Lock is active, rather than the normal unlock feedback.
• Symptom: If every credential is simultaneously rejected — PIN, app, RFID, fingerprint — and the lock was working correctly before, Secure Lock is the first thing to check from inside.

To disengage: enter the property via mechanical key (if available) or have someone inside turn the snib back to the unlocked position. Once disengaged, all digital credentials immediately resume normal operation.

The Airbnb & Rental Property Risk

For short-stay rental hosts, Secure Lock is one of the most operationally damaging scenarios possible — and it happens more than people expect.

Mitigation for hosts: If your lock has a physical snib, brief your cleaners and any regular property contacts to check and disengage it as part of the turnover process. Maintain a secure mechanical key held by a trusted local contact (not a guest key safe accessible to guests) for exactly this scenario. Some lock models allow the snib to be physically removed or disabled on installation — ask your installer if this is relevant to your setup.

For the broader picture on managing smart lock access at short-stay properties, see Using TTLock / McGrath for Airbnb in Australia and Using Igloohome for Airbnb in Australia.

Best Practice — Avoiding the Headaches

• Teach the household what the snib does and how to disengage it. Label it if needed. A piece of tape over the snib mechanism is a crude but effective reminder not to touch it.
• Keep mechanical key control tight. If keys are out there, Secure Lock provides no protection against the person holding one. Know exactly who has mechanical keys.
• Don’t rely on remote unlock as your only recovery plan if Secure Lock is likely to be used. Remote unlock will not work when the snib is engaged.
• Use Secure Lock intentionally — as a deliberate privacy or lockout mode — not as an everyday locking habit or alternative to simply locking the door normally.
• Rental properties: Include a snib check in your cleaner’s turnover checklist and maintain a local mechanical key contact for recovery.
• Ask at installation whether the snib on your specific lock model can be physically disabled if it’s not needed at your property. Some models allow this.

Related Guides

Not Sure Which Lock You Have or How Its Snib Behaves?

If you’re unsure whether your lock model has a Secure Lock snib, how to disable it, or what your options are after a lockout, our team can advise before you buy or modify anything.