Deployable cover

Deployable cover is a new piece of Covenant Equipment in Halo 3. Its symbol in the HUD is the outline of a dome with a dot inside it.

This shield is similar to the Stationary Shield Generator of the same type seen in Halo: Combat Evolved and Halo 2, except it can now be deployed anywhere. Additionally, the shield operates as a one-way shield - the user is able to fire through the shield from behind it with projectile weapons, but any bullets and other solid projectiles (except Carbine rounds and Needler) coming from the front will be deflected, however plasma fire and Spartan Laser are stopped by the shield from either side. This gives the user an enormous tactical advantage in exchange for being exposed from behind and to the left and right, whereas the similar Bubble Shield provides complete 360 degree cover, but cannot be fired into or out of.

The shield is deployed in the same manner as all other equipment in the game, and it will stay activated until it takes enough damage. The shield's health is represented by its color: it is normally blue, turns red as it is damaged, and finally deactivates. If left alone, the shield will regenerate to full health. To deactivate the shield permanently, the base must be destroyed. This only works in campaign. In multiplayer, the deployable cover will self destruct after a long period of time. It is also possible to make a "bubble" from two of these shields.

Trivia

 * Deployable cover is often used as an area to jump off of, as it is easier to use than the grenade jump for some players.