Constructors are small flying machines built by the Forerunners. Their only function is to repair Forerunner structures that appear to be damaged and can only be found on Forerunner worlds.
The Construction Beam is fired from the top half of the Constructor, however the constructors on The Ark fire their beams from the bottom. Sentinel Constructors also play another role as a security grid. When a Constructor is attacked, an unknown signal causes the Sentinel Launchers to begin deploying Sentinels. Constructors form an excellent security perimeter.
Constructors are devices similar to Sentinels in design, that mainly repair damage to any Forerunner structure they can find, using weak energy beams similar to Sentinel Beams. The beams are small, blue, and are harmful if they come into contact with an organism. It is unknown whether they will harm the Constructor itself, though.
The Sentinels will come to their aid if they are attacked, as they are ill-suited for combat, having no weapon systems of their own; however, their beams will damage you if you get caught in the path. They also use their beams to lower the shields on Pistons, allowing them to move throughout the Sentinel Wall quickly.
The Constructors first appeared in the beginning of The Library although only one or two can be seen floating around the corridors and into the air shafts. They also appeared in the opening moments of "Sacred Icon", where a swarm of them flies about trying to fix the platform you start on, then moves away further into the Sentinel Wall. They don't really affect anything in game, they show red on your reticle and you may shoot them if you like, although they won't bother you. If you jump in front of one in the beginning of "Sacred Icon", you can get hurt, though very little, by their thin beams depending on the difficulty level you are playing on.
- Sentinels have been seen using the Construction Beam in the level The Arbiter.
- Constructors are similar in appearance to the Plasma Pistol which could have inspired the design of them.
- In Sacred Icon, Constructors will open the Pistons for you if they are near them.
- In Sacred Icon, where you find the Grunt and the Jackal, if you look off the side into the chasm you will see an endless stream of constructors coming out of a bright hole in the wall.
- On Isolation and Construct, the Constructors can be sniped but their small size and constant movement makes this difficult.
- Although Constructors are never threatening, the player's reticle will turn red when passed over them.
- A player can get up close and even touch a Constructor on Construct. First he/she must overload the map with trip mines. When the map is overloaded the player must go through the hole where the purple lift beams are projected. He/she can then be easily touched by a Constructor but cannot be moved. They can be destroyed, mainly with a Spartan Laser or a Flamethrower. Note that even when one is destroyed another will immediately replace it in the same place (the debris from a destroyed Constructor fall from a full and complete one).
- In Halo 2, the Constructor's beam light is on the top part of its structure, whereas in Halo 3 the light is on the bottom half.
- Constructors appear to be able to compact into a smaller form, as their top and bottom halves appear to latch together. However, this has yet to be seen.
- On the level Sacred Icon, Constructors will scurry away from you if you approach them.
- Halo 2 (First appearance)
- Halo 3
- Halo Online
- Halo: Hunters in the Dark
- Halo 5: Guardians