What does the vault door do in fallout shelter?

Related questions

1. Can you revive Mr handy in fallout shelter?
2. Where is my Mr handy in fallout shelter?
3. How do you make your dwellers give birth?
4. Can all rooms be merged in fallout shelter?
5. What do bottle and Cappy do in fallout shelter?
6. What does Nuka Cola bottler do?
7. Can vault dwellers die?
8. What is the max level in fallout shelter?
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10. What is survival mode fallout shelter?

Tags

1. #dwellers
2. #increase
3. #health
4. #itself
5. #connects
6. #population
7. #vault
8. #occupancy
9. #upgrading
10. #stays
11. #wasteland
12. #maximum
13. #which