Lumber is a type of cargo found in Spirit Tracks. Lumber can be purchased from Whittleton after acquiring the Freight Car. Before being able to purchase Lumber, Link will need to bring Goron Iron to Whittleton, so that the tools needs to cut trees can be polished, allowing Link to purchase Lumber.
Link can bring Lumber to Anouki Village to help build a fence. Link will also need to bring the Bridge Worker from the Trading Post to Anouki Village to complete the fence. After the fence has been complete, Link will acquire a Force Gem. This gem opens up more Spirit Tracks within the Snow Realm, allowing Link to access Snowdrift Station.
Lumber on a Freight Car.