ORVIS - How to Use a Perfection Loop to Attach a Fly
The perfection loop is a useful knot for fly fishing. You can actually use it at both ends of your leader: first, to attach the butt section of the leader to the fly line, and then to attach the fly at the other end.
For lots more tips like these, check out:
The Orvis Fly Fishing blog: http://orv.is/1pIWKq7
The Orvis Fly Fishing Learning Center: http://orv.is/RZmNEd