I'm not a fly fisherman so I don't really know about fly line. I saw the nail knot was used to add tippet and leader to fly line. So I was thinking of using it to add leader to braided line . I bought a nail knot tool to try it out. I used braid, flouro and mono all had the same result,when pulling on the line the lines would separate . So I will go back to the uni to uni knot. So here is my question is fly line softer so the leader can bite in to it or am I missing some thing?

Fly lines are kind of like rubber-coated braid. A nail knot works since it can compress the rubber and keep it from slipping. Many of the newer fly lines have a loop at one or both ends to facilitate attachment of leaders and/or backing, so the nail knot isn't used quite as often as it once was.

Fly lines are kind of like rubber-coated braid. A nail knot works since it can compress the rubber and keep it from slipping. Many of the newer fly lines have a loop at one or both ends to facilitate attachment of leaders and/or backing, so the nail knot isn't used quite as often as it once was.

Thanks that makes sense to why the nail knot would not hold,but it sure a nice knot. 

Tie an overhand knot or two in the braid and then tie your nail knot above that. It'll hold, trim the tag end on the braid to 1/8 inch and you're good to go.

Tie an overhand knot or two in the braid and then tie your nail knot above that. It'll hold, trim the tag end on the braid to 1/8 inch and you're good to go.

Volfan thanks I will give it a shoot.