Figure 5:

With the stern, filler blocks are again an advantage to obtain the correct flowing shape of the counter and transom of the ship. As in the bow the additional gluing surface area is of great benefit. Although in both instances the use of nails in these filler blocks to hold planks is doubtful due to the soft nature of balsa, if you do use nails to fix the planks be sure they go into the actual bulkheads.