What trade did Douglass learn? What was his situation at the end of a year of working at this trade? What was unfair about this situation?

Hugh Auld apprentices Douglass to a shipbuilder named William Gardner. He is to learn calking. Time however is short so Douglass gets jobs with seventy-five different carpenters but he isn't taught much. Unlike the Free Black Carpenters, Douglas worked hard but didn't get paid.He gives all money to Mr. Auld. This is not fair! Douglass is beat up by white yard workers and must take time to recover.