Walls are basic obstacle for keeping out enemy infantry and vehicles. They are cheap and fast to build, and are the first lines of defence against the enemy's advance. They are often placed around key structures, such as construction yards, to keep out infiltrators and engineers. They are also often placed in front of certain base defences to draw fire, as building new wall sections destroyed in an enemy attack is often cheaper than repairing or building new base defences. Some base defences, like pillboxes and sentry guns, can not fire over walls.
Walls can not be directly targeted by air units without force-firing.
After a single wall hub is placed, another can be placed up to 4 tiles away in a straight line so that the sections in between the hubs are automatically filled for no extra charge. If an Allied or Soviet wall section is damaged, a new one can be built on top of the old one, which is not the case for Yuri's walls.
During the development of Red Alert 2, both Allied and Soviet walls had details painted in the colour of the owning player. This was replaced by a generic grey colour in the final version. Yuri's walls still have remappable sections, but they are unused.