by WhiteHat » 8 Nov 2004 21:57
although I don't know what type or even the jargon, you can get locks that work for a particular key that is given to a contractor building the property. when the owner's key is placed in the lock and turned, it causes some ball bearings to drop into small indentations at arround the 2 or 10 o'clock positions and the contractors key will no longer work. (so the contractor's key only lifts the pins up enough so that the ball bearings stay below the shearline)
this would mean that the owners key would have higher cuts than the contractors key. the only way I can think of the above described lock working is if there was a set of "master key" bearings and holes and using sequential keys would push one or mor bearings out of the way and allow the used key to work. what this would mean is that once you use one key, then go to another key, you wouldn't be able to go back to the first one. to be able to do that, there would have to be some mechanism that would re-insert the master balls/pins/whatever inbetween the drivers and key pins.
Oh look! it's 2016!