A wall was an upright structure used by architects and shipbuilders for defining an area and carrying a load. A wall could be for security, shelter, soundproofing, or, simply, for decoration. Walls were made from many different kinds of material. A unique wall was the transparency which was made of a transparent material, making it a kind of wall-window.
In 1836, during the Battle of the Alamo, the Mexican Army, under the command of Antonio López de Santa Anna, came over the north wall of the Alamo and defeated the defenders of the Alamo. Centuries later, when studying the battle by using a scale model of the Alamo compound, Julian Bashir considered reinforcing the north wall, the south wall, and any other place of the Alamo so as to keep the enemy out and give the defenders of the Alamo a chance of winning. (DS9: "The Changing Face of Evil")
On Talos IV, the Talosians built their cells with transparencies. In 2254, when he was a captive, Captain Christopher Pike tested the strength of the transparency by throwing himself against it. (TOS: "The Cage")