Graphical Construction Glossary >> Doors. >> Door Hardware >> Deadlock

A lock that is equipped with a deadbolt only, or a lock in which a bolt is moved by means of a key or a turn knob. It does not move into position by use of a spring. More correctly called by locksmiths a Deadbolt Lock.
Mortise Deadbolt Lock
A mortise lock that uses a deadbolt only.

A mortise deadbolt lock
Deadlock : A mortise deadbolt lock
Image provided by Hafele Australia Pty. Ltd.

It is well recognised that a dead bolt lock is a more secure option than a standard lock that has the spring assist close the bolt. The bolt is thicker and often it is quite a bit longer.

In my experience the fixing of deadbolt locks has always been an extra security measure to the standard locks. I can't remember ever just fixing one on it's own on a new job. there is always a lockable latch on the same door.

  • A deadbolt lock has to be locked on the outside with a key, so it can not accidentally lock you out. Unlike a nightlatch for example.
  • These deadbolts can be retracted during the hours when someone is at home and locked for extra security when the building is empty.
  • They come in three main flavours with variations in design, looks functions and security,
    1. The full mortice type seen above.
    2. The cylinder deadbolt type as seen below.
    3. The rim fixed one at the bottom of this page.

The full mortice type seen above can be used very simply with Keyed Alike and Master Keyed or any of the other Key System. Others can work with Electronic Keyless Systems and Electric Strikes.

A deadbolt lock, can have single key or double key
Deadlock : A deadbolt lock
Image provided by Hafele Australia Pty. Ltd.

Above is a very common cheaper option. They are easy and quick to fit, but it must be done right and the strike should be fitted as snug as possible. Any slop will give that extra space for a jemmy to work.

For the most part these bolts come with a cylinder on the outside and a turn button on the inside. They also come in Twin Cylinder designs. This means no quick turn knob on the inside but a key is used. So we then come to the question of safety v. security.


  • The theory that a key operated lock on the inside of a home is a good idea, is that if a thief enters your home, say through a small bathroom window then he won't be able to steal much if he can't get out through a normal sized door.
  • Another possibility is that if your door has a glass panel near the lock, then even if a thief breaks the glass and reaches the inside of the lock he still can't open it because it needs a key to do so.


  • Following any sort of security rule then the key can not be left in the lock or in an obvious an easily reached place, otherwise you might as well use a turn knob.
  • The concern with safety is that any lock that require a key to open and particularly and exit door is a safety risk in the event of a fire inside the building.
  • In the event of a fire, people may be disorientated, blinded by smoke or overcome by fumes, the last thing they need is to be looking for a key to escape.

So the choice, boiled down to it's simplest terms and worst case scenarios is between your property or the life or well being of yourself or your family.

Look at the photo below: would you sooner be turning the knob {marked F. ) or looking for a key in an emergency?

Some idiot at Wikipedia has written this this uncorroborated statement on the issue:-"Some fire departments suggest putting the key on a small nail or screw near the door at floor level, since the cleanest air is at floor level and you may be crawling to get to the exit, thus placing the key where it is easiest to find."

What a lot of tripe! There would not be a fire department in the world that would suggest this! They'd tell you to change the lock, and in no uncertain terms.

Deadlock: A composite shot of two sides of the same door. The lower silver lock is a deadlock.

This photo is from my door locks introduction page so if you have not seen it then go there to pick up the terminology the the letters are referring to.

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Adam Smith 1723-1790

"When we build, let us think that we build for ever."John Ruskin 1819-1900

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Please Note! The information on this site is offered as a guide only!  When we are talking about areas where building regulations or safety regulations could exist,the information here could be wrong for your area.  It could be out of date!  Regulations breed faster than rabbits!
You must check your own local conditions.
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