Vault doors may look like big lumps of solid steel, but they have some of the most extensive security engineering features found in any single object. Vault doors are extremely heavy, often weighing several tonnes, and have a primary purpose of delaying access to bulk cash loads, high-value goods or classified assets.

While the use of heavy but movable barriers to protect items of value has origins almost as old as humans themselves, the first ‘true’ vault doors for strong rooms were developed in the early 1800s. The first patent for a ‘modern’ vault door was filed in 1826 by American iron chest and safe maker Jesse Delano in New York City. As the safe and vault sector grew with the growth in general levels of wealth, urbanisation, crime and industrialisation (including the increased availability of steel), more companies were founded to capitalise on the opportunities to provide these types of products to banks, post offices and safety deposit centres.

By the early 1900s, many different industrialised countries had local companies that manufactured vault doors for strong rooms. The most successful vault door manufacturers of this period included Britain’s Chubb, Tann, Ratner, Chatwood, and Milners; the USA’s Diebold, Mosler, Consolidated, American, Sargent, York, Herring‑Bell and Hall’s; France’s Fichet, SLP, CFCS and Groupe Bouchard; Germany’s Panzer, DWG, Schwabe & Söhne, and König; Holland’s LIPS, Van der Wiel and NFVA; Sweden’s Rosengrens; and Switzerland’s Wiedemar, Bauer and B. Schneider; amongst others.

Aside from the high-security combination locks, time delay locks and alarms, modern vault doors are constructed of multiple layers of different materials, such as steel, reinforced concrete, bitumen, copper, aluminium, manganese steel and rubber. Each material is intended to delay or mitigate attacks with specific types of tools used by threat actors. For example, the outer steel layer may require an angle grinder with a metal-cutting disc, but this tool would be ineffective against bitumen.

Vault locking mechanisms also have specific security measures to protect them from precision or brute force attacks. This often includes tempered glass panes, attached to steel cables, that are designed to shatter if penetrated. This automatically sets off anti-burglary locking devices called ‘dead relockers’. Additionally, doors often have angled steel plates designed to deflect power drill attacks targeting the lock.

Bank vault doors are ultimately designed to mitigate and protect against three main attack methods used by serious criminal threat actors:

1. Forced entry using a range of tools
2. Lock picking to release the locking mechanism
3. Opening of the door by an authorised employee under duress