Shield Door

From Halopedia, the Halo wiki

One of the Shield Doors on Snowbound.

Shield Doors are Covenant made "doors" that are able to allow people and machines through while keeping plasma and gunfire out. They are similiar in design to energy shields that the Jackals wear.

There are several on the in past Halo games and they appear in Halo 3 on multiplayer map Snowbound.