The jib topsail is the longest triangular sail and is rigged to the ship before the other fore sails. Use a toothpick or pin to dot a bit of glue on the end of the bowsprit and the top of the mast above the topsail. Lay the thread attached to the jib topsail so they are anchored in the glue, with the thread taut as shown. Once the glue has grabbed, leave the threads to dry.
When the threads that hold the sail in position are dried in place, use sharp scissors to trim the excess thread away at the mast and the bowsprit. If a short length of thread remains, apply a bit of glue and glue the thread around the edge of the mast or bowsprit.