The master key is a now product that making by ourselves. The key can open many locks in the same way. Just like, 20 X 100 locks, there are 20 keys can open 20 X 100 pcs locks, and anyone key in the 20 pcs, can open any lock in the 100pcs. Of cause, the three key appertain any lock cann't open other lock, but if u want they can open the other locks, we also can do it. So the product suits many corporation that want to manage the department. And now, go with the technology pullulating, we can produce another key, one key, can open the different locks of 20 group which have 100 pcs locks in each group.