Shield wall is an ability granted by the W.A.R. Suit.
The wearer of the W.A.R. Suit becomes a a piece of full cover wherever they stand. Both allies and enemies may take advantage of this cover. If an ally already has high cover from an enemy, careful use of the Shield Wall ability may break the enemy's line of sight to that trooper. Moving or attacking will cancel the effect. It does not offer the wearer of the W.A.R. Suit any advantages, and they may draw additional fire.