Let me say, I'm not a safe-cracker or in any way 'dodgy'. I bought one of these for the carer who looks after my elderly grandmother so that she'd never not be able to let herself in, without the risk of losing the key.
However, whilst it secures to the wall very firmly & the keys sit nicely inside, & it's easy to choose a unique code, with a very small amount of 'testing', it's surprisingly (not to mention shockingly) simple to open without knowing the combination.
To test it, I even set a random combination in total darkness & then opened it within a couple of minutes.
Thus I would NOT recommend this product except for the very minimum security. Theoretically if it were placed in a high-view area to dissuade a dishonest person from cracking the code, this may be a solution. But to my mind, it does not do the job it was purchased for.
In response to a number of comments, in particular "Angryoap" (on 5th July '12), doubting the ease at which this lock is crackable, this review is now edited to remove the "method" by which it can easily (& quickly) be opened by someone not in possession of the code.
I accept that what was previously included in this review may not have been completely sensible on a public forum such as this, but at the time, I felt obliged to inform potential purchasers with the full situation of what I considered to be a waste of money (& why).
Finally, it's possible that some of these locks have better security than others & I can only go by the product that I received, back in December '09.