Objects used and are in AoT(Cannons)

Cannons:

Cannons were the primary weapon used to engage Titans before the development of the 3D maneuver gear.

Despite the ability of a cannon to blow a Titan's head off in one shot, half of all Titans will merely regenerate their heads; the only certain way to kill a Titan is to destroy the nape of its neck. Cannons are still used in static defense poistions, most notably on the Walls and near gates during Wall breaches. As such, they are used most often by the Stationary Guard.

The cannons contain two different rounds: pomegrenades and grapeshots. Pomegrenades are high explosive rounds used to attempt to kill a Titan by destroying the nape of the neck in the blast. Grapeshots are the more traditional cannon round and are mostly used to slow down Titan advances with their wide dispersion shots.

Before firing, the cannon must be solidly fixed to prevent the recoil from blowing it off the tracks. Wall-mounted cannons also possess the ability to fire directly downward, which can allow them to release punishing volleys of fire at Titans with no threat of reprisals.Later developments led to railroads encircling the entire Wall, allowing cannons to bunch together and focus fire.Prior to the breach of Wall Maria, Wall-mounted cannons had limited mobility and could only fire from one point inside or outside the Wall.

During the breach of Trost District, the Colossal Titan disabled the railroads on top of the Wall to prevent reserve cannons from being brought in.