For any flying jibs, ones not hanked to a stay, there was a danger of dropping the sail in the water and trapping it under the bow while setting and dropping it. The traveler allowed the jib halyard to be brought inboard while being handled to minimize this risk. There are contemporary pictures of boats moored in New York Harbor with the flying jib hoisted in stops allowing it to be set by pulling on the sheets and breaking them. Again, this and the bowsprit traveler allowed the jib to be handled inside the boat. Detail copied on my scratch built 1:32 scale longboat model.