what are the extra holes in the tumbler?

[Elminster]

I pulled apart my first lock last night, I have been waiting to get to lowes for a 1/2 inch dowel/ plug follower, and I noticed that right next to the holes for the pins is another row of holes. this second of holes is only a couple of mm deep and the diameter is smaller than either the upper pin or lower pin. What is this second set of holes? this was on a kwik-set dead bolt ($15 at lowes).

[Jow]

Are these holes in the plug or the lock body?

[Keyring]

The holes are for construction keying. They are to allow ball bearings to fall into on the first use of the real key by the new house owner, which renders the builder's master key ineffective.

[Elminster]

The holes are for construction keying. They are to allow ball bearings to fall into on the first use of the real key by the new house owner, which renders the builder's master key ineffective.

How would filling these holes with ball bearings make a master key ineffective? As I understand it a master key just positions the pins at a different shear line, so a master keyed lock would have 3 parts to some of it's pins. the extra line of hole in the plug is too small for any of the pins to go into, which is why I was wondering about it. If I am missing something please let me know I am genuinely curious.

[zeke79]

It's not masterkeyed, it is construction keyed. Do a search for construction keying.

[2octops]

Three ball bearings in each chamber are used instead of master wafers. The builders key has the deep cuts on it, keeping the ball bearings in the pin chamber of the plug. Once the home owners key is used, it puts the bearings above the shearline nad when the plug is turned, the bearings fall into the extra lil holes.

[Keyring]

I probably shouldn't have used the words 'builder's master key' in this context. I understand that some construction keying systems use a masterkeying approach, but the way I picture the ball bearing version, I guess the builder has a different key for each house

[Elminster]

Three ball bearings in each chamber are used instead of master wafers. The builders key has the deep cuts on it, keeping the ball bearings in the pin chamber of the plug. Once the home owners key is used, it puts the bearings above the shearline nad when the plug is turned, the bearings fall into the extra lil holes.

that explains it. I remember when I bought my house they told me to turn the key to the left the first time I used it and then to the right to unlock the deadbolt.......now I know why.

thanks

[Stash]

So that's what those are... I've been wondering for a while, but since they didn't do anything I was beginning to think it was just some defect in the lock and that I would look stupid if I said something about it.
~Stash