Forum:Best 'z' key uses

The 'z' key doesn't seem important to finishing the game. (I've only played to level 4 though) To practice using it I tried to stack oil drums on top of the car of Nuko Cola machine at the Springvale Red Rocket gas station in order to get on the top of the roof. I failed but was able to get on top of the Cola machine and on top of a barrel placed on top of the car just under the roof. Anyone had more success? I doubt there's anything up there but what the hell? alatari