Why Won’t My Deadbolt Lock? (Snib Explained)

If your lock will not allow the deadbolt to extend or lock, the reason may be a small security feature called a snib.

This is normal behaviour and usually does not mean the lock is faulty.

What Is a Snib?

A snib is a small part inside the lock that helps improve security.

When the door is fully closed, the door frame pushes the snib into the lock.

This tells the lock that the door is properly shut.

Once the snib is pushed in:

-The spring latch is secured.

-The lock allows the deadbolt to extend.

Why the Deadbolt May Not Lock

If the door is open or not sitting properly in the frame, the snib will not be pressed.

When this happens, the lock blocks the deadbolt from extending.

This is a safety feature designed to prevent the lock from engaging when the door is not closed correctly.

Common Reasons This Happens

The snib may not be pressed if:

-The door is still open

-The door is not fully closed

-There is a large gap between the door and the frame

-The door is misaligned

-This is sometimes seen on large or heavy communal doors where the gap between the door and frame is wider than normal.

How to Check

Try the following:

Close the door firmly.

Make sure the door is fully sitting in the frame.

Try locking the door again.

If the door locks when it is fully closed, the snib is working correctly.

Important

The snib is a security feature, not a fault.

It helps prevent the lock from being forced and ensures the deadbolt only engages when the door is properly closed.