The Shield Wall is an upgrade of the Hvy Wall, and is available in Tech Level 4. Like the name suggests, it is shielded, giving it twice as many hit points as the Hvy Wall. It costs 5 Ore per unit, and players can build Gates to let their units pass through.
Unlike Turrets, Walls and Gates do not change appearance when upgraded.
"Shield Walls, which may be upgraded from Heavy Walls at Tech Level 4, are practically impervious to all but the most concentrated firepower — and their regenerative shielding makes them even more versatile. Note that Shield Walls are self-powered, and needn't be built in the vicinity of Power Cores. "