I recently played with a friend who said you can use the maritime harbor to trade 2:1 in both directions. I said this wasn't true, but couldn't disprove him in the rule book. The rules say:
The exchange rate of 2:1 only applies to the resource shown on the harbor location.
Suppose you're on a 2:1 wood trade.
(1) You can trade 2 wood cards for 1 grain/ore/sheep/brick card.
(2) You can trade 2 cards for 1 wood card. (2 grain for 1 wood. 2 brick for 1 wood etc.)
Can you only do (1), (2), or both. Which is correct?