Locks you should not use

The padlock shown below has a shackle (the U-shaped curved metal rod) with a diameter of about 7 or 8 mm. That shackle is too easy to cut with bolt cutters.


Combination lock

However, I suspected that I could easily defeat this lock by another method. Using hand tools I found in my shed, I was able to open this lock in 2½ minutes. I think I could improve on that time if I chose better tools and practiced opening the lock. And I'm no expert: this is the first time I have ever tried to defeat any lock.

I think it's too easy to beat a lock with plastic dials like you see in the picture.




A number of years ago, news spread that tubular key locks could be opened using a disposable pen. The method did not take any special skills, and could be done fairly quickly. But how many thieves know about this trick? I can't even guess about that.


tubular key lock

Does this mean that such locks should be thrown away, if already owned? Not necessarily. I still use that lock shown above, partly because my bike is not worth much. But I would not purchase another lock with that kind of key.

The lock can be oriented so passersby can't readily see what kind of key it uses.

Such a lock could be used redundantly with another lock, as shown below.


Double padlocks lock-up after a bicycle commute

Not all thieves will know the trick to beating these locks or be carrying the correct sized disposable pen. Even if a thief is prepared for this lock, it still would cost extra time to defeat it. Also, the double padlock setup shown here might look so difficult that a thief would not even stop to check if the lock takes a tubular key.




I probably should put all cable locks, except the really thick and strong ones, in the category of bad locks. Many thieves know how to cut them fairly quickly.