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Posted by Smitty Two on February 15, 2008, 9:37 pm
> Can one open a combination lock without knowing the combination?
>
> I'm helping to clear out a building which is about to be torn down,
> and in the office is a sheet metal cabinet, with a door on the left
> side and two shelves inside, and on the right side is a larger door
> with a safe-style lock on it, a single dial, a black plastic wheel
> with numbers on it.
>
> By no means is this worth the money that a professional would charge
> -- we never even locked it when we were using the building, or we
> would still remmeber the combination -- but it seems like a
> challenging project to me.
>
> It got locked somehow and no one remembers the combination. I've
> heard that it is still possible to open them. That the movies are not
> entirely wrong, with someone using a stethoscope to hear the
> "tumblers" "fall" into place.
>
> OTOH, I had a toy safe, when I was about 20 years old, twenty!, and it
> was clear plastic inside, and I could see the gears turn when I turned
> the dial on the front, and even in this toy, there were no tumblers to
> fall as one or more of the three wheels (the gears) each with a notch
> in one place, got their notches lined up. Only when all three notches
> were lined up, could one open the plastic safe.
>
> There was nothing to hear until the last second when it opened.
> Rotating the knob and the gears made no special noise at any point
> (except maybe a noise could be heard after one reversed direction of
> the knob and when a cog on a gear close to the front hit a stop on the
> next gear back and it started to turn. but what has the number that is
> at the top of the dial at that moment got to do with the combination
> number? Is that it? Can the latter be deduced from the former?) I
> don't see how it could be.
>
> From Wikipedia "Some rotary combination locks can be manipulated by
> feel or sound in order to determine the combination required to open
> the safe. More sophisticated locks use wheels made from lightweight
> and soft materials such as nylon, which reduces this vulnerability."
> This seems like nonsense. Why does it have to be "sophisticated" when
> my 4 dollar plastic toy safe couldn't be opened by feel or sound?
>
> One webpage says "Despite the tried-and-true design of the safe, it
> contains a fundamental weakness: Every safe must be accessible to a
> locksmith or other authority in the event of a malfunction or
> lock-out. This weakness forms the basis of safecracking." It says
> "every" but does that really apply to something that probably costs no
> more than one or two hundred dollars new now.
>
> BTW I don't think this is a fire safe or a real burglary safe. It
> bangs too much to have fire insulation in it (and I saw it when it was
> unlocked and open, come to think of it) and anyone could cut into it
> with a hack saw, or a boy scout can opener, or puncture a hole with a
> big screwdriver.
Sounds identical to a gadget we had to open after the boss died.
Locksmith wanted around three or four hundred dollars. After two weeks
of discussion, a couple of people just pried it open with a crowbar or
something. It's basically sheetmetal, as you noted.
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