What you do is put pressure on the lock opening system (either a lever or simply pulling the lock apart) and you twiddle each number ring until it revolves completely. It does take a while but i've done it a few times now. The reason why you put pressure on the mechanism is because the instant the correct combination is achieved the lock either opens or there's a slight movement preventing the combination rings from turning further. Furthermore, because it will open as soon as the correct combination is achieved, it allows you to rotate the lowest ring at a reasonable pace, as opposed to clicking it once and checking, then again, and checking. It does take the piss! there's 9999 combinations for a 4-ring lock, and 999 for a 3 ring, i've only had to open 3 ring ones, and it's taken me around half an hour. A 4 ring one should take about 5 hours to go through entirely... you know, that's a long time... this, however, would take between half an hour to 1 hour to open.