Go buy a heat shrink tube! Available in electronic accessories stores! When it is not heated, it is like 5 mm. After heating, it will shrink to 1 mm! The outer skin of household batteries is sealed with this thing! Very cheap and easy to use! Another way is to heat the needle with wax, and then make a small hole in the middle of one leg; while heating, insert the needle into the other end while it is hot but not too hot! Then cut the appropriate length and insert it into the other hole to apply glue!