Locked But Not Deadlocked: What Selective Deadlocking Means

Most people think a door lock is either locked or unlocked.

With some locks, there is another important difference: the door can be locked, but not fully deadlocked.

This is where selective deadlocking comes in.

Selective deadlocking means the lock can be used in more than one way. In normal locked mode, the door is locked from the outside, but someone inside can still get out using the internal snib, lever or turn. In deadlocked mode, the internal snib, lever or turn is disabled, and a key is needed to unlock the door from the inside.

That difference matters.

A door may have a deadlock fitted, but that does not always mean the door is actually deadlocked.

Having a Deadlock Is Not the Same as Being Deadlocked

This is one of the biggest misunderstandings with door locks.

A lock may be capable of deadlocking, but that function only works when the lock has actually been deadlocked.

For example, many locks can be used in normal locked mode. The door is locked from outside, but the inside snib or lever still works. This is convenient and safer for people inside the home because they can get out without looking for a key.

But from a security point of view, that is not the same as being fully deadlocked.

When the lock is fully deadlocked, the inside control is disabled. The lock cannot simply be opened by turning the inside snib, lever or turn. A key is needed.

That is the main difference.

Why Deadlocking Exists

One of the main reasons for deadlocking is to stop someone from reaching through and operating the lock from inside.

For example, some doors have glass panels in the door or beside the door. If the door is only locked in normal mode, someone could break the glass, reach through, turn the inside snib or lever, and open the door.

When the lock is properly deadlocked, that inside control will not open the lock. A key is needed.

That is the security benefit of deadlocking.

But it is also the safety concern.

If someone inside the home needs a key to get out quickly, that can become a problem in an emergency.

This is why deadlocking is always a balance between security and safe exit.

Common Places You May Find Selective Deadlocking

Selective deadlocking is common on many residential doors, especially sliding doors and security screen doors.

On some sliding door locks, there may be an inside lever, snib or turn that locks the door without using a key. If the same lock also has a key cylinder on the inside, it may be able to deadlock as well.

The inside cylinder is important. A key cylinder on the outside allows the door to be locked from outside, but an inside cylinder is usually what allows the lock to be deadlocked so that a key is needed from inside.

Security screen door locks often work in a similar way.

If the screen door is locked using the internal snib, it can normally be unlocked again using the snib. But if the door is locked with the key, the snib may be disabled. At that point, the lock is deadlocked and a key is needed to unlock it.

This can be useful on a security screen door, especially if the screen or mesh could otherwise be damaged and the snib operated from outside.

But again, the same feature that improves security can also make emergency exit harder if people are inside and the key is not close by.

Some Locks Have More Than One Locking Position

Some locks are designed with more than one key position.

One position may lock the door from outside while still allowing someone inside to exit using the internal snib. Another position may fully deadlock the door, meaning a key is required from both sides.

The problem is that many people do not realise there is more than one position.

They simply turn the key all the way until it stops, thinking they are just locking the door. In some cases, they may have actually deadlocked it.

This can create a common situation.

One person leaves the house and locks the security door from outside while someone else is still inside. The person inside expects to be able to use the snib as normal, but the door has been deadlocked and now they need a key to get out.

That does not always mean the lock is faulty. It may simply be the way that lock is designed to work.

Locked Mode Versus Deadlocked Mode

A simple way to think about it is this:

Normal locked mode is usually better for easy exit.

Deadlocked mode is usually better for security against someone reaching through and operating the lock.

Neither mode is perfect for every situation.

When people are inside the home, easy exit is important. A lock that requires a key to get out can create a safety issue if there is a fire or another emergency.

When nobody is home, deadlocking can give extra security, especially where there is glass near the door or where someone could otherwise reach the inside control.

This is why many people use deadlocking mainly when the property is empty, such as when going away or leaving the home unattended for a longer period.

Deadlocking Is a Choice

A selective deadlocking lock does not normally deadlock automatically.

That is a good thing.

If every lock automatically deadlocked every time the door was locked, it could create a serious safety risk for people inside the home.

Instead, the deadlock function usually has to be selected by the user.

This is where the confusion starts.

A person may look at the door and say, “I have a deadlock.”

That may be true.

But the more important question is:

Is the door actually deadlocked right now?

If it is only locked in normal mode, the deadlock function may not be active.

The Glass Panel Example

Glass near a door is a good example of why this matters.

If there is a glass panel in the door or next to the door, a normal locked mode may not stop someone from breaking the glass and reaching through to operate the inside snib, lever or turn.

In that situation, the door is locked, but it may not provide the full deadlocking benefit.

If the lock is properly deadlocked, the inside control is disabled and a key is needed. That makes this type of attack harder.

But again, there is a trade-off.

If people are inside and the door is deadlocked, they may need the key to get out.

That is why the right way to use the lock depends on the situation.

Keying Locks Alike Can Reduce Confusion

One way to make locks easier to manage is to have suitable locks keyed alike.

If the front door, back door, sliding door and security screen door all use different keys, it can be confusing and slow to find the right key.

When locks are keyed alike, one key can operate multiple locks.

This does not remove the safety concern of deadlocking while people are inside, but it can reduce confusion and make the locks easier to use.

For many homes, keying locks alike can be a practical improvement, especially where there are several external doors.

The Main Thing to Remember

A door can be locked without being deadlocked.

That is the key point.

Selective deadlocking gives you a choice. Used one way, the lock provides normal locking while still allowing easier exit from inside. Used another way, it provides stronger deadlocking security, but may require a key to get out.

The most secure setting is not always the safest setting when people are inside the home.

If you are not sure how your lock works, it is worth having it checked. A locksmith can explain whether the lock is simply locked, fully deadlocked, or capable of both.

A to Z Locksmiths provides locksmith services across Geelong, the Bellarine Peninsula and the Surf Coast, including rekeying, lock replacement, sliding door locks, security screen door locks and general home lock advice.