Learn how to tie the nail fishing knot with this knot tying instructional video. The nail knot is a popular and time tested fishing knot to join fly line to leader. Use of a hollow tube instead of a nail makes for easier tying. 1. Lay a nail or hollow tube against the end of a fly line. Set the butt section of a leader against the line and the tube or nail. Leave an aextra 10" - 12" of it's tag end to tie the fishing knot. 2a. Hold all three pieces together with left thumb and forefinger and make six to eight close together wraps, working left to right, back around the leader, line and the nail or tube. 2b. Pass the tag end though the tube or space made by the nail and remove the tube or nail. Pull the tag end to snug up the coils. 3. Pull both ends of leader simultaneously to seat the knot firmly onto the fly line. Trim the tag end close to the nail knot.