1. As you can see from the inside of the security door, there are two screws at the lock position. Open it with a screwdriver to remove the door handle inside.
2. Don't go out. At this time, you can see an iron needle with the length of 10. You can take it off by hand. It's simple.
3. Then change the iron pin from the original 10 to 6: 5, so you can go to the hardware store and cut it for one yuan.