Keep all valuable or hard-to-replace documents in a safe-deposit box: birth, adoption, marriage, divorce and death certificates; property deeds; vehicle registration documents; stock, bond or savings certificates; a copy of your will; a household inventory; and all insurance policies. Keep a list of the box's contents at home.
You can deposit your own box with your bank on payment of a fee and they will look after it for you. You keep the key - the bank will not have one. Some banks offer special safety deposit facilities where you rent one of their boxes in a purpose-built vault. But this costs a lot more. You have one key and the bank has another - both are needed to open the box. If you lose your key you may have to pay a hefty fee to have the lock drilled open - but the bank will need positive proof that it is your box.
Check your householder's policy to see if it covers the contents of your safe-deposit box, or ask the bank if it offers insurance.
When a box renter dies, the bank will only allow the box to be opened by a person who proves that he has proper authority, which will usually be the executor or administrator of the estate. A copy of the death certificate and proof of identity is required.