And lo on Fri, 20 Jun 2008 16:39:56 +0100, Darren New <dne### [at] sanrrcom>  
did spake, saying:

> scott wrote:
>> Locks can be designed to be opened by two different keys (usually a  
>> unique key and a master key common to several locks).
>
> We have cool locks on the doors of our houses, designed especially for  
> builders. Basically, all the locks can be opened with the master key,  
> until the first time you use the lock-specific key that the builder  
> gives to the new homeowner.  So, the first time you unlock your own  
> door, you lock the builder's master key out. I have only the vaguest  
> idea of how they accomplish that.

They use little ball-bearings between the pins, when the builders use  
their key they shear at the top of the bearings and the bearings stay in  
the plug. When you use your key you raise the pins so the shear line is at  
the bottom of the bearings and when you turn they fall into holes set in  
the plug and are thus removed.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message