From Die2Nite Wiki
The Bank is where the town stores all the useful items to be shared by the community.
Items are found in the World Beyond by entering a controlled territory and scavenging for resources. These items can then be placed in the bank for the use of the community. Combining some items can create new items. Defence objects placed in the bank provide protection for the whole town. Resources placed in the bank can be used for construction of useful buildings.
You can take five items from the bank before you are locked out of the bank for 15 minutes. During Chaos Mode, the limit for taking items increases to 10. Taking a second ration at the well counts towards this limit, although your first ration does not.
All items taken from the bank are recorded in the Great Register.
Containers and Boxes