Second Mordor Catapult

 This really is a second catapult, not just the first with an extra helping of muck and rust.

Note that one wheel was damaged on the way from the Black Gate, hence the different colour of the timber.

As these giants launch their payload, the beam swings up and crashes into the cross beam.

This batters the whole contraption forward at an angle so that the blade at the front digs into the ground.

Which is why we have mud and even a sod of grass collected on the front.

Talking of angles, how on earth did they aim the thing?
All I can assume is that they used crowbars to lever the back end, either right or left.

See below for mud, tuft and replaced wheel.