The best place to open the lock is to talk to your thief trainer. There is one thing I can improve my unlocking skills. Npc will tell you where you should go now according to your current points. It was very useful 300 years ago. After 300 hours, you can open the wicker box in Zhaoman Village in our swamp. You can only dig for jewels by yourself. It's too expensive to buy it from. Just follow what the technicians taught you 300 years ago.