Unloading coal from truck - GIF

[Frank S]

So does it tip sideways to get the last of the coal out?

Most likely it has an "A" floor or what would be called an upside-down V so the coal falls either to one side or the other, but I doubt it since it appears even the rear can be opened as well. What I don't understand is why he is dumping the coal on the ground in the first place instead of in a bin or some other receptacle