You can use the common braided leader loops on a Barrio fly line, but these have disadvantages on all fly lines by holding dirt and causing hinging. Adapting one of the following methods will always help to improve turnover and presentation.
The Constriction Knot
This is a simple method of attaching most types of backing line, furled leaders and leader materials to a traditional type of PVC coated fly line like the Barrio.
(1) Overlap the fly line and backing line by around 12 inches.
(2) Take the end of the backing line and fold it over itself and the fly line to form a loop and grip the point of overlap (A) firmly between the thumb and forefinger of the right hand.
(3) Bring the end of the backing through the loop half a dozen times.
(4) Carefully draw the turns together while sliding the whole knot towards the tip of the fly line. With the turns of the knot touching, pull steadily on both ends of the backing until the knot grips the fly line tightly. Check the security of the knot by pulling the backing and fly line firmly in opposite directions. When satisfied, trim the ends closely.
(Please note) The constriction knot should not be used with hollow braided nylon backing line, nor is it suitable for fly lines with multi-strand or monofilament cores and harder coatings.
The Gray's Loop
The Gray's Loop is a version of the Constriction knot used to attach a semi-permanent loop of nylon monofilament to the end of a traditional PVC coated fly line like the Barrio. This nylon loop facilitates a loop to loop connection with the fly leader. Such a loop might last a whole season before needing replaced.
Follow the same procedure as for the Constriction Knot, but with a doubled length of monofilament nylon. Starting with a length of about 18 inches (half a metre) of nylon makes it easier to pull the knot tight. Also start with as small a loop as possible, held between the right thumb and forefinger (figure 1), if you want to create a small loop (although a loop of anything up to around three inches long works fine) Use a minimum of three turns.
Carefully draw the knot together while sliding the whole knot towards the end of the fly line. With the turns of the knot touching, pull steadily on both ends until the knot grips the fly line tightly. Check the security of the knot by pulling steadily with a finger in the loop. When satisfied, trim the ends closely. The strength of the nylon will vary with the weight of fly line and breaking strain of leader. As an approximate guide I would suggest the following:
Fly Line #3 / Loop nylon 10 lb / Leader nylon 2 to 5 lb
Fly Line #4 / Loop nylon 10 lb / Leader nylon 3 to 5 lb
Fly Line #5 / Loop nylon 10 lb / Leader nylon 3 to 5 lb
Fly Line #6 / Loop nylon 12 lb / Leader nylon 4 to 6 lb
Fly Line #7 / Loop nylon 12 lb / Leader nylon 6 to 8 lb
Fly Line #8 / Loop nylon 15 lb / Leader nylon 8 to 10 lb
The Perfection Loop
This is a reliable leader loop which lies in line with the leader and the loose end can be trimmed very close to the knot.
The Perfection Loop is not as difficult to tie as it seems at first sight. Use the thumb and forefinger of the left hand to grip the knot while manipulating the loop with the right hand.
The Reel Knot
This is a simple and reliable knot which can be used to secure backing line to the reel.
For added security, take the backing round the reel drum twice before tying the knot.
After pulling the slip knot tight, trim the loose end but not too close to the knot.
The Loop to Loop
A simple and effective method of attaching a leader to the fly line, avoiding the wear and tear on the butt loop which might result from the repeated tying of knots.