andrex66 wrote:Could someone explain what the second row of holes are for? They don't reach all the way through the cylinder,are they used for some sort of trap for the driver pins?
Ah. Those are for a special setup called "construction keying".
There are a number of threads on the topic if you search around -- but, in essence, it's a way of providing a "temporary" key that can be used while your house is first being constructed. It's usually done by inserting a small set of ball bearings between the top and bottom pins (
i.e., the ball bearings go where you would normally put a masterkey wafer if you were master-keying a lock). Various manufacturers have different trade-names for these; Kwikset calls them "Protecto-Key" balls.
The "builder" key is cut shallower: when it is inserted, the ball bearings stay inside the plug, just above the bottom pins.
However, when you take possession of the house and you first use your "owner" key, its cuts are higher: it pushes the ball bearings up into the "bible", above the plug. As the plug rotates, that second set of holes passes underneath, the ball bearings fall down into the second set of holes and are trapped... and, from that point on, the "builder" key will no longer work: you've effectively removed the "master-key wafer".
If you look closely, the second set of holes are slightly smaller than the main pin chambers: this prevents the drivers from also falling in and jamming the cylinder.
).
