Vault-Tec, when constructing their Vaults made sure that their inhabitants are well protected from outside threats. One of the key pieces of engineering that protected the dwellers was the Vault door.
 Door Variants
 Interior doors
The Vault Door is a type of electro-mechanical door used in the Vault-Tec Vaults for creating physical barriers between corridors, rooms, and stairways. The hatch is a heavy steel door, of either one or two pieces, supported in a heavy steel frame built into a wall and powered by concealed powerful hydraulic motors.
 Standard door
A typical door used in the Vaults, composed of two pieces that connect and seal (with the use of special interlocking cones) when the door closes. An emergency override handle is placed above the connection seam. Under normal circumstances, when a hatch is locked, only an experienced locksmith could lockpick the hatch. Each door is operated by hydraulic motors that effect 3300 lbs of pressure when operating the door.
Doors are designed with three safety features. The first is a caution zone marked by yellow lines on the floor. The second is an automated system that reverses the door if it detects an obstruction, and attempts at closing the door a few moments later. If the obstruction remains under the door, it will continue repeating this motion until powered off or the door finally closes. The final feature is a power box next to the door, which can be used to shut off electricity to the bulkhead and seal it. Under normal circumstances, the lamps on the power box are green. If the power to the door is cut using the switch, they glow red.
 Security door
This model is identical in function and safety features to the door above, except there is a centrally painted white vertical band with a stop sign and the words "No Access - Authorized Personnel Only". There are downward pointing chevrons above and below the text.
 Maintenance hatch
This is a one-piece hatch. Hydraulic motors swing it 90 degrees on a hinge when opening. On one side of the hatch, there are two circular indicators. When the hatch is closed, both indicators display diagonal red lines on a white background. As the hatch is opening, the indicators display OPEN in red text on a white background, while the other shows STAND BACK in red text on a black background.
 Vault Blast Door
A Vault requires proper sealants against radiation and other hazardous elements that may be created in the event of a nuclear war, to properly protect its inhabitants. Vault-Tec used a number of different door models in their shelters, the most common being the 'Seal-N-Safe' Vault Door Model No. 343 (denoted as such in the Vault 15 townmap).
 'Seal-N-Safe' Vault Door Model No. 343
Most common model, this door was first used in the demonstration Vault beneath Los Angeles. It had a smooth outer surface and opened outwards, rolled to the side by an extending mechanical arm. It was a very compact design, usually followed by a long air lock, ending in a high security door, with two layers of steel and a slab of lead in the middle.
 Unspecified model
A different model was used in the East Coast and the Mojave Wasteland Vaults; this particular one opened inwards, with the use of a hydraulic arm. The door is shaped like a cog. When opened, a siren activates and a large mechanical arm swings down from the ceiling, opening the vault door from the inside. The door is pulled inward and rolls off to the side allowing access. This method produces a high volume metal grinding due to the weight of the door.
- Despite having no visible keyboard, the door access panels on the east coast use a password (though it may be that the password is input through speech, as shown by there being a large speaker mounted on the panel's face).
- The door in Vault 108 cannot close by activation of the access panel. Instead, the player can activate the door itself, making the door impossible to open or close any further without the use of console commands.
- The East Coast and Mojave Wasteland inward opening vault doors make less sense than their west coast counterparts in terms of effectiveness as a blast door. The vault door's purpose was to withstand the blast of a nuclear weapon and act as a seal from the environment outside. The west coast doors would accomplish this end more effectively as they closed from the outside, either against mechanical stops or a friction wedge design which, when acted on by the pressure wave and blast of a nuclear weapon would force it harder against it's stops strengthening the sealing effect of the door. Inward opening doors would not do this, possibly exposing its occupants to outside contamination. This may have been a deliberate design choice by Vault-Tec. While most west coast vaults open directly to the outside, most of the east coast vaults were built with their entrances within existing caves which would limit the door's exposure to direct blast pressure and allow a cheaper and less complex door design to be used.