Walls are the most straightforward form of fortification in Middle-earth, and are able to be built by most factions, or already naturally stand at the stronghold of certain Fortress-maps. Walls in the BFME games are either "normal walls" or "rampart walls".
Walls that are built from Wall Hubs are "Normal walls", since they most commonly appear in the progression of a long Skirmish, and are the only walls that can be constructed and repaired. These walls do not serve as battlements, are easy for siege engines to destroy, and can always be scaled and breached by Corsairs, Spiderlings, Corrupted Men heroes with the "Climb Wall" ability, and goblins.
The gates of normal walls, such as Arnorian gates or constructed Wall Hub gates, can be passed through by any unit type as they lack an archway.
Rampart walls are broad walkways upon which archers and siege machines can stand, and attack enemies from. They are very durable against siege engines, and usually have 5000 health-points per "unit". Ladders and Siege towers can only be used against rampart walls, but units who can scale normal walls (listed earlier) cannot climb up rampart walls on their own.
Only the fortresses of Helm's Deep, Minas Tirith, Isengard, and Minas Morgul are fortified with rampart walls. At Minas Tirith alone, trebuchet-expansions and Arrow tower expansions can be constructed on them. At Helm's Deep, only postern gates can be constructed. At Isengard and Minas Morgul, there are no wall-expansions.
Rampart walls are continuous, and do not have corner-parts. Their gates are more fortified than gates of normal walls, and have ceilings. However, because of the ceilings' height-restriction, Siege Towers, Mumakil, and Balrogs cannot pass through them.