Darning Needles for Nail knots
You can buy large needles with large eye openings at craft stores for under a dollar. They are a great tool for nail knots... just lay the eye along the fly line, then lay the butt material over the eye and flyline with the ends pointing in opposite directions. Wrap the butt back over itself, the line and the needle.
Thread the end of the butt after 6-8 wraps, then pull the needle out. This creates a nail knot in seconds (with a little practice).
The needle fits nicely in a foam flybox.
Note: some needle styles work better than others. I've had the best luck with longer needles with a short hole at the eye. The length gives you more to grab onto. Once you find the style that works best for you, they are a cheap and effective solution to tying nail knots in the field. The very best kind are those long threading needles with holes on both ends... use a peice of heavy backing to tie one end to the inside of your chest pack, vest, etc.