Bank Vault Doors: How They Work, Who Made Them and How Time Locks Changed Bank Robbery

A bank vault door is a machine as much as a door. Swing one open and you’ll find inches of laminated steel, a ring of bolts, a crane hinge and a clock. Here’s how they work, who built them, and how that clock stopped robbers taking cashiers hostage.

Bank vault doors at a glance

Also called	Vault door; strongroom door in British usage
Main parts	Door, vestibule (frame), bolt work, crane hinge, pressure bars, combination locks, time lock, relocking device, day gate
Thickness	Mosler’s standard range around 1960: 1¼, 3½, 7, 10, 12 and 16 inches; special doors thicker
Weight	20 tons or more for large bank doors; a reported 100 tons at the Cleveland Federal Reserve
Shapes	Rectangular and round (circular)
Major makers	Mosler, Diebold, York Safe & Lock, Herring-Hall-Marvin (USA); Chubb, Hobbs Hart, Chatwood (UK); Fichet (France)
Time locks	Sargent & Greenleaf from 1874; Yale and Hall from 1875
Standards today	UL 608 (USA); EN 1143-1 (Europe)
Where to see one	Old bank buildings now used as shops, bars, gyms and museums

How a bank vault door works

Mosler’s 1951 specification sheet for its standard seven-inch bank vault door reads like a parts list, which makes it the clearest way to see what’s actually inside a vault door. Every part below is taken from it.¹ (A vault is a room built round a door like this one; how it differs from a safe is explained in vault vs safe.)

Two principles run through all of this. The first is that the hinge only hangs the door: once it’s shut, the bolts and the frame hold it. Linus Yale Jr. made the same point in 1856, writing that the hinges of his bank doors were used only for their proper purpose and that “no reliance is placed on them for security”. The second is that the lock doesn’t hold the door either. It controls the bolt work, which a handle throws, so the lock is spared the strain of moving heavy bolts.² That’s why one door can carry two combination locks and a time lock at once.

Fire doors and burglary doors

Not every vault door guarded money. Makers also sold lighter fire-resistive doors for record rooms. Diebold’s 1933 range was rated from 29 minutes to six hours in Underwriters’ Laboratories furnace tests; when UL tested an old-style uninsulated steel plate door in 1927, it failed after 21 minutes, when the inside of the vault reached 300 °F (149 °C).³ Mosler’s six-hour record-room door of around 1960 had seven 1-inch bolts and an emergency escape handle inside, “a turn of which will permit immediate escape of anyone locked in the vault”.⁴ Burglary doors are a separate class. Today UL 608 rates vault doors in the United States, and EN 1143-1 grades strongroom doors in Europe.⁵⁶

Round and rectangular vault doors

Round doors came later. In 1890 the Cary Safe Company of Buffalo was selling a “new patent screw door” bank safe whose round door had a heavy thread cut into it and was screwed home by gear wheels, which made it “air and water tight”.⁹ Round vault doors followed in the early 20th century and became, in one modern maker’s words, “long the world symbol for security”. The same maker notes that the early doors relied on sheer mass of metal.¹⁰ Diebold’s round door at the Winona Savings Bank in Minnesota carries a notice giving its weight as 22½ tons, with a four-movement time lock behind glass.¹¹

Rectangular doors never went away. The 1914 Diebold door above is rectangular, and so was Mosler’s standard seven-inch door of 1951.¹ Around 1960 Mosler listed circular doors as one option in its Century range of bank vault doors.⁴ Some doors combine both, like the round door in a square frame at the Helena branch of the Federal Reserve shown at the top of this page.

“The open view reveals the heavy bolts and intricate jeweled movements of the timelocks.”

Mosler Safe Co. catalogue, c.1960

That line explains a lot. The same catalogue says the bolts and time locks “fascinate most bank customers and give an added feeling of strength and security”.⁴ Vault doors were made to be seen open during banking hours, with glass over the bolt work and a day gate behind, and the round door was the most theatrical version of that display.

How thick and heavy is a bank vault door?

Thinner than most people think, and heavier. By 1951 Mosler built its seven-inch door from layers of open-hearth steel, hardened plate to resist drills and copper to resist the cutting torch.¹ Its standard doors around 1960 ran from 1¼ to 16 inches thick.⁴ In 1924 a Cleveland maker of vault reinforcement noted that the lowest burglary insurance rates applied to any door 10 inches thick, yet “it is not uncommon” for banks to buy doors of 20 inches or more.¹² The figures below are as given in the sources cited; a dash means the source gives none.

Door	Thickness	Weight
Linus Yale Jr. chilled-iron bank door, 1856	1¼ in (3 cm)2	–
Mosler No. RLD-7 bank door, 1951	7 in (18 cm); 12 in at the bolt frames1	–
Mosler standard range, c.1960	1¼ to 16 in (3 to 41 cm)4	–
Diebold round door, Winona Savings Bank, Minnesota	–	22½ tons (20 tonnes)11
Chubb circular door, Commercial Banking Co. of Sydney, 1920s	–	25 tons, according to the banner on its crate
Federal Reserve Bank of Cleveland, 1923	–	100 tons (91 tonnes)13
Fort Knox Bullion Depository (Mosler), 1936	21 in (53 cm)	20 tons (18 tonnes)14
Bank of Spain gold vault (York), 1936	–	Some doors over 14 tonnes15
Mosler blast door, Greenbrier bunker, c.1960	19.5 in (50 cm)	Over 20 tons16
New York Fed gold vault entrance cylinder	–	90 tons, turning in a 140-ton frame17

American “tons” here are short tons of 2,000 lb (907 kg); a British ton is 2,240 lb (1,016 kg). Weight alone never made a vault secure. The same 1924 handbook argued for “balanced protection”: walls, floor and roof should resist attack as well as the door, and it warned that thousands of bank vaults had heavy doors in walls with only a fraction of their strength.¹² In other words, a heavy door in a weak wall is mostly for show. For a sense of scale at home, our guide to how much an old safe weighs covers ordinary safes and floor loading.

Who made bank vault doors?

Vault doors were a specialist trade within the safe industry, and a handful of firms built most of the big ones. These are the names you’re most likely to find on a wheel hub, a plate behind the glass or a time lock case.

Maker	Base	Vault work
Mosler Safe Co.	Hamilton, Ohio	Credited by the Hamilton press in 1936 with the Fort Knox vaults; the Manufacturers Trust round door (1954); the National Archives vault (1952)18
Diebold	Canton, Ohio	A 363-tonne safe deposit vault for San Francisco in 1875, shipped in 40 railway cars, with three doors and five locks19
York Safe & Lock Co.	York, Pennsylvania	Founded in 1882; Federal Reserve vaults in New York, Boston, Philadelphia and Chicago; the Bank of Spain doors20
Herring-Hall-Marvin	New York, then Hamilton, Ohio	Vault doors from the 1860s; push-button “5-Star” vault entrances in 1956821
Chubb	London	Large safes and strongroom doors at Glengall Road from 186622; circular anti-blowpipe doors, like the one shown below
Hobbs, Hart & Co.	London	Locks, safes and strongroom doors; part of Chubb from 195623
Fichet	Paris	The Crédit Lyonnais vault in Paris, begun in 1876, with some 7,800 Fichet safes24

In America the trade shrank to a few firms. Diebold took over York’s safe and vault business, patents and branches in January 1946, after York had spent the war making guns and armour.²⁵²⁰ When Diebold bought Herring-Hall-Marvin in 1959, the Justice Department argued that the two were among only three American makers of bank vault equipment.²⁶ The third, Mosler, was bought by Diebold in October 2001.²⁷ So all four of the big American names in the table above ended up under one roof, Diebold’s.

In Britain the same doors are called strongroom doors. Alfred Hobbs, the American who picked the Bramah and Chubb locks in 1851, said his London firm won much of the lock work of the government and the Bank of England; the business became Hobbs, Hart & Co. and later part of Chubb.²⁸²³ His story is told in the Great Lock Controversy of 1851. From 1960 Chubb’s 3½-inch anti-blowpipe strongroom door, made at the Hobbs Hart works in Leyton, replaced Milner’s equivalent in the Chatwood-Milner range.²⁹ In Paris, the Crédit Lyonnais vault was described as the largest in Europe when fire wrecked the building above it in May 1996; only two strong cupboards were reported damaged.³⁰

Time locks: the clock that beat the kidnappers

A combination lock has one weakness no engineer can fix: somebody knows the combination. By the late 1860s and early 1870s good bank locks were hard to defeat in a night, so robbers went after the people instead. Masked gangs seized cashiers and bank officers at home and forced them to open the vault after hours, sometimes with fatal results.³¹³² A series of such robberies, in which bank managers were kidnapped, is what finally persuaded American bankers to buy time locks.³³

Timeline

• 1831 William Rutherford of Jedburgh patents a clockwork lock for bank doors.
• 1858 Amos Holbrook’s time lock guards banks at Milford and Holliston, Massachusetts.
• 1874 The first Sargent time lock is fitted at Morrison, Illinois.
• 1875 Yale and Joseph L. Hall of Cincinnati enter the time-lock business.
• 1877 Sargent & Greenleaf and Yale agree to share the market and fix prices.
• 1880 Hall forms the Consolidated Time Lock Co.
• 1894 Diebold makes its first time lock.
• 1927 Consolidated closes.
• 1929–1940 Sargent & Greenleaf records no domestic time-lock sales.

Sources for the timeline: Holbrook from Day and Erroll; Yale, the 1877 agreement and Consolidated’s closure from a time-lock collectors’ history; Hall from the history of his firm; Diebold from the collectors’ survey of its locks.^33313637 Our history of safe lock mechanisms covers the locks themselves, and Hall’s Safe & Lock the Cincinnati side of the story.

Two failed raids, 1875

The new locks were tested almost at once. In May 1875 a masked gang broke into the Great Barrington, Massachusetts, home of Frederick Deland of the Mahaiwe Bank, seized him and his family, and took him to the bank to open the vault. The bank had recently fitted a Sargent & Greenleaf time lock, and the robbers could not open it. Deland wrote that when the gang’s leader asked about the lock, he told him what it was for:³⁸

“To prevent the bank from being robbed in the way you are trying to now.”

Frederick Deland, letter of 1875

That July, on the night of the 5th, robbers tried to make the cashier of the National Bank of Barre, Vermont, give up the combination of the bank’s locks. They were defeated by a “chronometer lock” fitted to the safe only days earlier; the cashier, left tied up at home, freed himself and raised the alarm.³⁹

Where the combination alone still opened the vault, the method worked. Around midnight on 25 January 1876 five masked men entered the home of John Whittelsey, cashier of the Northampton National Bank in Massachusetts, bound the household and held him until about four in the morning, when he gave up the keys and the true combination. The gang took money and securities estimated at a million and a quarter dollars, much of it belonging to safe deposit customers.⁴⁰

Did time locks end hostage robberies?

They ended the night-time version. With a time lock running, nobody could be marched to the bank at midnight to open the vault, and a bank could share the combination with its staff at far less risk to them.³² What a time lock can’t control is who stands beside the door when it opens in the morning. In December 2004 a gang held the families of two senior Northern Bank officials hostage in Northern Ireland and told the officials to go to work as normal; about £26.5 million left the bank’s Belfast headquarters in a van.⁴¹ Crimes of this kind, now often called tiger kidnappings, are the modern form of the problem the time lock was invented to solve. Our guide to old safe combination locks explains how the dial side of a vault door is used, and our article on time locks covers the clockwork side: the makers, the movements and how collectors date them.

Famous vault doors

Central banks don’t say much about their doors, so most of the famous figures come from the firms that built them. More on the vaults behind them is in our comparison of the most secure bank vaults in the world.

The Bank of England is more private still. Its present vaults were built during Herbert Baker’s rebuilding of 1925–1939, several levels below ground, and today hold about 400,000 bars in nine vaults.⁴³⁴⁴ Journalists shown round in 2012 reported keys about three feet long, not something you’d slip into a pocket.⁴⁵ In Cleveland, the Federal Reserve’s 1923 vault door is reported to weigh 100 tons.¹³ And in Washington, Mosler built a 50-ton vault in 1952 to lower the Declaration of Independence and the Constitution below the National Archives exhibition hall each night; it was removed in a renovation in the early 2000s.⁴⁶⁴⁷

The most public vault door of all is in Manhattan. When the Manufacturers Trust Company opened its glass-walled branch at 510 Fifth Avenue in 1954, the industrial designer Henry Dreyfuss and the Mosler Safe Company designed a round stainless steel door that stood in plain view of passers-by on Fifth Avenue. New York’s Landmarks Preservation Commission made the banking floors, door included, an interior landmark in February 2011, as the owner prepared to turn the building into shops.⁴⁸

What happens to old vault doors?

If you own, or want, an old vault door

• Plan the move first. A bank door weighs tons and needs rigging, a clear route and a floor that can take it. Our guide to moving or getting rid of an old safe explains who does this work.
• A door is not a vault. Doors were made to be set into masonry to the maker’s plans, and a door on its own is a display piece.¹ A certified rating does not survive modification of the door.⁵⁴
• Service the locks before you ever close it. Have a qualified safe engineer check the combination locks, the relocking device and any time lock. If a door is already shut and nobody can open it, see locked out of an old safe.
• Value depends on maker, condition and buyer. Our guide to whether old safes are worth anything explains what drives prices.

Not sure who made yours? The maker’s name is often on the wheel hub, on a plate behind the glass or on the time lock case. Send us photos of the door, its plates and its locks and we’ll help you identify it.

Frequently asked questions