The perfection loop is an incredibly useful knot because it allows you to quickly add a new leader to the loop at the end of a fly line. But as this great video from Tightline Productions demonstrates, the perfection loop is also an effective way to tie a streamer to the end of your tippet. By using a loop instead of the standard, say, clinch knot, you give the streamer more freedom to move in the water, which gives it a more lifelike action
Tim Flagler ties the knot four times in this video, showing you exactly how to hold the line and seat the knot. After you watch this, break out some tippet material and practice for ten minutes, and you’ll be proficient at it forever.