Vault materials and vault doors have also evolved. Steel doors were used in the past, but because they were readily cut by torches, alternative materials were tested. Massive cast iron doors resisted acetylene torching better than steel. Later, aluminum and glass became popular replacements for metal because they are lighter, do not conduct heat as well, and are shatter resistant.
The most common today is concrete. It is heavy, durable, and non-conductive. Concrete vault rooms can be opened up to allow in light or air, or closed off completely if need be. They can also be lined with paper or other material to keep out moisture and prevent damage to stored items.
Gold has been used for thousands of years as a form of currency. It is hard to steal and easy to recognize even when taken from its setting. The technology needed to recover gold from old coins or jewelry has only recently become available at a reasonable cost. Modern gold recovery techniques include chemical treatment, heat processing, and physical manipulation.
In conclusion, gold vaults are safe, affordable, and reliable means of protecting valuables of all kinds. They can also provide some measure of security through obscurity - people may think twice about robbing an unmarked bank vault, for example.
The walls of most modern bank vaults are built of steel-reinforced concrete. The concrete used is a very thick combination with metal fragments mixed in to make the material almost drill-proof. The door is likewise made of similar extremely indestructible concrete. The keypad and alarm system on a vault door are usually concealed within the concrete structure of the door.
When a bank closes its doors, it typically sends out letters to its customers notifying them of the closure. If a customer has an account at the closed bank, they will usually be given the option of transferring their funds to another branch or some other location. Otherwise, their money will be lost when the bank's vault doors are locked up at night and transported by truck to a new location.
Almost all large cities have many banks occupying single buildings. These are called "branch banks". Each branch of the bank serves a different geographic area of the city; therefore, they must be located in different locations. Smaller towns may only have one bank, which will often be the main office of a larger corporation that operates several branches in various parts of the country.
Banks use security systems to protect their properties. These systems are designed to detect intruders and report their presence. They can be found at bank offices, vaults, and even at certain retail stores.
The barrel-vault, groined (or four-part vault), and dome vaults were the three types of vaults employed. The barrel-vault was by far the most common type of roof vault in England and on the continent from the 11th to the 14th centuries. It was also used in some parts of Europe into the 15th century, but it was being replaced by the gable or hip-roofed house. The groined vault was used mainly in northern France and Belgium; it was also popular in Italy and Spain. The dome vault was used mostly in Russia and Asia.
Barrel vaults were usually made of wood and covered with clay. They were hollow inside and had round ends. The ribs that held up the vault were placed at equal distances from one another. Sometimes there were as many as four rows of wooden beams with the spaces between them filled in with clay or stone. The barrel vault was used for large rooms because it could bear a great weight above the floor.
Groined vaults were made of brick or stone and often included walls around the perimeter of the room underneath the vault. These walls would help support the weight of the ceiling and prevent it from collapsing under pressure such as that caused by many people standing on a small area of floor space.