The Bottom Line
Understand transform and shape nodes
DAG nodes have both a transform node and a shape node. The transform node tells where an object is located; the shape node describes how it is made. Nodes can be parented to each other to form a hierarchy.
Master It Arrange the nodes in the miniGun_v03.ma file in a hierarchical structure so that the barrels of the guns can rotate on their z-axis, the guns can be aimed independently, and the guns rotate with the turret.
Solution In the Outliner, MMB-drag the left_gunBarrels node onto the left_housing node. MMB-drag the left_housing node onto left_mount, and then MMB-drag the left mount onto the turret node. Do the same for the right_gunBarrels, housing, and mount nodes. ...