You need a safe deposit box to protect items and documents from natural disaster and theft. It will prevent you from losing the important documents in a move, or from accidentally throwing the documents away.
What should I put in the box?
Anything that would be hard to replace if lost or damaged, or anything that would cause trouble if lost or damaged. Keep any insurance policy originals, any birth, marriage, or death certificates and information you would otherwise not want to lose if your home were to burn down or flood.
What should I leave out of the box?
Don't put anything in the box you would need during hours the bank is closed, or in the case of an emergency. Don't put your Will in the box, or your power of attorney, as these are documents that may be required for others to access the box in the event you die or become incapacitated. Give the originals of these important documents to your attorney, or a close trusted family member or friend, and keep copies in the box.