A smokebox is a part of a train where smoke from the engine goes out.
A smokebox is a part of a train, so it makes people think of trains and travel.
Examples:
The smokebox is where the train lets out smoke.
The smokebox on the old train is big.
The train driver checks the smokebox.
The smokebox is like the nose of the train.
The smokebox is where the train breathes out smoke.
The smokebox is always in front of the train.