Sentence:  By the time the Mauretania was ready for launching a total weight of 16,800 tons was standing in the berth, and this represented the heaviest weight that had ever been sent down the <WSD>ways</WSD> up to that time. 
Meaning of the word marked with <WSD> tags:  The timbers of shipyard stocks that slope into the water and along which a ship or large boat is launched.