Wall

Walls are the most basic defenses, serving as barriers to prevent ground units from going through.

Tiberian Dawn

 * Sandbags (Tiberium)
 * Chain link fence
 * Concrete wall (Tiberian Dawn)

Tiberian Sun

 * Concrete wall (Tiberian Sun)
 * Firestorm barrier
 * Firestorm wall section
 * Laser fence (Tiberian Sun)

Tiberium Wars

 * Wall (Tiberium Wars)
 * Sonic repulsion field
 * Laser fencing (Kane's Wrath)

Tiberium Alliances

 * Wall (Tiberium Alliances)
 * Laser fence (Tiberium Alliances)

Red Alert

 * Sandbags (Red Alert)
 * Barbed wire
 * Concrete wall (Red Alert 1)

Red Alert 2

 * Fortress walls (Red Alert 2)

Red Alert 3

 * Fortress walls (Red Alert 3)

Generals

 * Wall (Generals)