Containment field device

The containment field device is a Forerunner restraint device. It is comprised of two rings which emit an energy field which encircles and restrains a prisoner or any held object. Similar technology is also used by the Covenant.

The Apex
The Apex installation of the Flood-controlled Shield World possessed a containment field device. The device also worked as a transporter pad, and was operated by vocal commands. When containment was activated a ring would hover above the held object, connecting the containment field to the ring on the floor. When the field was disengaged, the upper ring would fall into a socket in the floor. There was a similar device on the surface of the Shield World, though it is unknown if it was just the receiver for the teleporter. The Covenant used this particular containment field device as a holding cell for Professor Ellen Anders.

Sanctum of the Hierarchs
A similar, though not identical device was seen in the Sanctum of the Hierarchs within High Charity. Likely a Covenant application of the Forerunner technology, it was used to hold 343 Guilty Spark in a stasis field in which it was unable to move. Instead of a clearly visible torrent of energy, the energy field was less visible. The rings emitting the field were also stationary.

Trivia

 * This device is aesthetically very similar to the Force cage used to hold Obi-Wan Kenobi captive in Star Wars: Episode II: Attack of the Clones.