Containment doors

The Containment doors are a set of large, metallic containment devices seen in the Steambot Barracks room of SkyTown, Elysia. When active, the doors appear in a semicircular shape with shingled plates. Faint mechanical noises can be heard from within while it is closed. It opens at the middle, and retracts into the ground in a fan-like fashion.

It houses the Steamlord, which is released in the event that an intruder is detected in the room. As Samus enters and attempts to leave, the metallic piping system is triggered and locks her inside. The containment doors open and a pod floats out, releasing the Steamlord. The doors remain retracted into the floor for the rest of the game. Later, when Samus acquires the Boost Ball and uses the Kinetic Lock in the room, a half-pipe emerges from the same floor hatch that the Steamlord emerged out of.

Scans
"Containment doors sealed. Faint mechanical sounds can be heard coming from within."

Trivia

 * The sounds emerging from the doors resemble those made by the Decepticons from the Transformers films.