The shield-wall formation was a commonly deployed defensive formation used by the armies of Middle-earth. To complete this formation troops would line up shoulder to shoulder and use their shields to form a wall while waiting for the enemy's charge. It is similar to (and often mistakenly referred to as) the Phalanx formation.
Use of the "wall"Edit
The shield-wall was commonly employed by the forces of Gondor especially during the Third Age. The troops that were most known for their employment of this technique were the Guard of the Fountain Court. These elite troops of Gondor would form a near-impenetrable wall of shields upon which their foes would break. There was one thing that could break the shield wall, however. It is said that the great Mûmakil (Oliphaunts) could break through any formation that stood against them.
This method of using the "wall" is used in The Lord of the Rings: The Battle for Middle-earth by the Gondor soldiers to massively boost defence, but decrease speed by 50 %