In fly fishing, a Perfection Loop is probably most often used at the butt end of a tapered leader. It allows the leader to be securely attached, via loop-to-loop connection, to a loop at the end of the fly line. Although not as streamlined as the more traditional nail knot, the loop-to-loop connection does make it quick and easy to change leaders right on the stream.
If your fly line doesn’t have a loop, you can always add a braided loop to the end of it to connect to the leader’s perfection loop. Or, nail knot a short length of heavy monofilament to the end of the fly line and then tie a small perfection loop in the end of the mono. This too will allow for a loop-to-loop connection to the leader.
Less commonly, a perfection loop is used to secure the tippet end of a leader to a fly, allowing for greater movement and range of motion.
Although perfection loops aren’t hard to tie, people often have difficulty remembering how to tie them. But a little repetitive knot tying can do wonders in this regard.
We’ll start with a length of paracord as it’s easier to see than monofilament. A little ways back from one end, make a loop. Form the loop so the end of the cord passes under the running line and ends up in your right hand. With the thumb and index finger of your left hand, pinch the intersection and then bring the end over top of the first loop and behind the running line to form a second loop. Re-grip with your left hand to hold both loops in place. Once again, the end of the line should end up in your right hand.
Next, place the end of the line between the two loops and then get hold of all three with the fingers of your left hand. At this stage, the knot should look something like this.
Coming up from below, reach through the first larger loop with the thumb and index finger of your right hand, and get hold of the second, smaller loop pulling it down and through the first loop. Pull on the finished loop and then the tag to firmly close the knot. If done correctly, the tag end should exit the knot at a nearly 90 degree angle to the running line.
Here's the perfection loop again but this time with smaller diameter fly line that’s obviously seen better days.
Form a loop so one end goes beneath the running line. With that end, go over top of and around the first loop and secure both loops in the fingertips of your left hand. Then, pull the end over top of the first loop but beneath the second and grip it with your left hand fingertips. Reach through the first loop to grab the second and pull it through. Close the knot by pulling on the finished loop and the tag. Check to make sure the tag end exits the knot at approximately 90 degrees.
Snip the tag end off, but not too close, leave just a little nubbin sticking out for security. The front and back of the finished knot should look something like this.
Here, I’m going to use pretty standard leader butt material, 30 pound Maxima Chameleon. Form the first loop by placing one end underneath the running line. Go around the first loop to form a second loop. Then, slip the line between the two loops and grip them all with your left hand. Reach through the first loop to pull the second loop through. After loosely seating the knot, by pulling on the loop and then the tag end, place the loop around something sturdy and pull on the running line to draw the knot completely closed. As before, snip the excess tag end off, leaving a small nubbin sticking out at about a 90 degree angle.
To tie on a fly using a perfection loop, insert the tippet through the eye of the fly and, while maintaining a 6” long tag, form a loop with the line in your right hand going beneath the line in your left. At this point, the fly should be located between the loop and the fingers of your right hand. Go all the way around the first loop to form a smaller secondary loop then place the tag between the two loops. Pull on the right side of the first loop to increase its size, you’re actually pulling the running line through the knot. Pull until you have enough room to drop the fly through the first loop, while it’s held by the second. Close down the enlarged first loop by pulling on the running line. You want to draw the loop all the way down to very close to the hook eye. The more you pull, the smaller the finished loop will be. Pulling on the tag end will also help to close the loop down even smaller. Firmly seat the knot by tightly holding the fly and pulling on the running line. Finally, snip the excess tag end off, leaving a small amount standing proud of the knot.
The Perfection Loop works quite well for attaching flies, particularly streamers that benefit from a wide range of motion.