There are several ways to tie fly fishing line to the leader, including the use of a nail knot while attaching the leader directly to the fly line. Discover how to make things easy with a loop at the end of the fly line with help from an experienced fly fisherman in this free video on fly fishing equipment.
I'm Steve Oxley from Denver Angler and now I'm going to show you how to tie the fly fishing line to the leader. There are several ways this can be done. One is using the nail knot and attaching the leader directly to the fly line. The bad part of that is every time you change leaders you are clipping away at your fly line and sooner or later you compromise your fly line. The best and easiest connection for people is a loop at the end of the fly line. You can buy fly lines that have welded loops already built in to them or you can have your local fly shop attach a monofilament butt section and put a loop in that. To do the loop to loop connection buy a leader that's already got a loop on the end of it and most fly shops stock leaders with loops on them. Place the loop of the leader over the top of the loop at the end of the fly line, double up the leader, and push it through the loop on the end of the fly line and pull the tag end all the way through so when you pull them together it forms a figure 8. Attach it, pull it down like that and if it hasn't formed the figure 8 you have done it wrong and you have to do it again and that is how you attach the leader to the end of the fly line.