Door

Doors are movable barriers used to cover up openings; typically, such barriers are attached to the very openings they block. They are used by virtually all factions in the Halo universe.

Appearances
Below is a list of the various door shapes and colors seen in the Halo games.

Halo: Combat Evolved

 * Pillar of Autumn: Two-part human-made doors.


 * Halo: N/A


 * The Truth and Reconciliation: Two-part Covenant doors.


 * The Silent Cartographer: Triangular, tri-segmented Forerunner doors.


 * Assault on the Control Room: Triangular, tri-segmented Forerunner doors.


 * 343 Guilty Spark: Triangular, tri-segmented Forerunner doors.


 * The Library: Massive Forerunner security doors. Several smaller types.


 * Two Betrayals: Triangular, tri-segmented Forerunner doors.


 * Keyes: Two-part Covenant doors.


 * The Maw: Similar as in The Pillar of Autumn.

Halo 2

 * Cairo Station: High-tech automatic doors with a light indicating their status.


 * Outskirts: Un-passable grey doors with yellow upside down triangles. Large doors in the highway tunnel.


 * Metropolis: Similar doors as in Outskirts. Several other metropolitan type doors.


 * The Arbiter: Rectangular Forerunner doors with a blue square in the middle.


 * The Oracle: Similar doors as in The Arbiter.


 * Delta Halo: Doors with an oval eye.


 * Regret: Same doors as Delta Halo.


 * Sacred Icon: Forerunner Pistons.


 * Quarantine Zone: Large Forerunner vehicle doors containing multiple segments which spin 90° and retract upwards.


 * Gravemind: Multi-layered Covenant doors.


 * Uprising (level): Triangular Forerunner doors.


 * High Charity: Similar doors as in Gravemind (level)


 * The Great Journey: Same as Uprising (Level)

Halo 3

 * Sierra 117: N/A


 * Crow's Nest: Heavy bunker-style doors, which are opened with door control buttons, remarked by a marine as being "old tech", as the base was built in the 21st century.


 * Tsavo Highway: Large bunker doors of Crow's Nest, highway doors.


 * The Storm: Various futuristic factory complex doors, most openable with a button.


 * Floodgate: Same as in The Storm.


 * The Ark: Triangular, tri-segmented Forerunner doors.


 * The Covenant: Triangular, tri-segmented Forerunner doors.


 * Cortana: Flood Portas -- large, sphincter-like orifices.


 * Halo: Triangular, tri-segmented Forerunner doors.

Trivia

 * The object John-117 rode to Earth in the beginning of Halo 3 is apparently a some sort of Forerunner door, part of the Forerunner Dreadnought.