There have been many people who have reviewed and tested safe combination locks, including large organisations such as Underwriters Labatory and the British Standards Institute. It is the same with door locks, and insurance grade keyed padlocks. However, when I was recently asked to provide a secure combination lock for a set of factory gates, there was nowhere to turn to.
After buying and testing several combination padlocks, I decided to publish my notes, and at that point, I decided that it would be worth testing some of the lower end locks too.
If you use any of the locks given a poor score, you should probably think about upgrading them if your security is important to you. The advice for opening them is limited to very basic manipulation, the kind of thing that most people could work out in a few minutes if they were so inclined. No fancy tools are needed.
I am releasing the paper as “linkware” – you may have a personal or business copy, in exchange for a link back to here. If you are a locksmith, and would be interested in a full copy of this paper, please leave a comment with your website details, and, please link to this site. I will verify it and send you a full copy of the paper to your registered email address, which contains the manipulation process for each of the locks featured. Feedback, as ever, is welcome.