by Steve99
I can understand the OP's confusion.On first reading of the rules it does not make it clear that the Shipping line is a seperate card offering its own building action.
So when you first see the ability to sell X goods using the Shipping Line on each of the ships you can easily be mislead into thinking that the shipping line action is an action offered by the ship itself.
It would have been much clearer to have explained this in the rules itself, rather than merely reference the shipping line in the buildings overview sheet, as that assumes that you know it is a building in the first place.
Of course it makes total sense, now that we know.