The need to connect two lines is common in angling, typically when joining mainline to leader or tippet. And whether you chase tuna offshore, hunt bass on a southern pond, or trick trout with a dry fly, knowing how to connect two lines is essential.
But as any experienced angler can tell you, that point of connection is usually the weakest link of the chain connecting your reel to the fish.
More often than not, you can look for the culprit of a line failure at the mainline-leader connection.
That said, there are better and worse options for connecting two fishing lines, but most tend to be pretty specialized.
Want to know how to connect two fishing lines?
Table of Contents (clickable)
- 1 Knot Know-how: What Makes a Good Connection?
- 2 Three Knots for Line-to-Line Connections
- 3 Final Thoughts
Related: Top Fishing Lines By Type
Knot Know-how: What Makes a Good Connection?
When you’re thinking about how to connect two fishing lines, there are several questions that you need to answer to pick your best knot:
- Do I need the knot to pass through the guides on my rod?
- What line types am I connecting?
- How different are the diameters of the two lines?
Let’s break that down to see why these answers are critical.
Do I need the knot to pass through the guides on my rod?
If you’re a fly angler who needs to connect your mainline to a leader or leader to tippet, you’re not overly concerned about the size of the knot you tie. Chances are, it’ll never come into contact with your rod’s guides, and whether it can cleanly pass through them just doesn’t matter that much.
Similarly, if you’re trolling for muskie or pelagic species like king mackerel, tuna, or shark, your mainline to leader connection needs to be rock solid, but it can be pretty big since casting isn’t the name of the game.
But if you’re a bass angler who’s throwing a length of fluorocarbon or monofilament leader to reduce visibility, a castable knot matters a lot. Ditto for pier and beach anglers who’ll be looking for long, efficient casts.
When you need the knot to slide through guides, size matters; choose a slim knot.
What line types am I connecting?
Material science and physics are everything when it comes to knots, a simple fact we’ve discussed before.
And while monofilament exhibits what engineers and scientists call a “high coefficient of friction,” meaning that it “bites” against itself and holds a knot like gum in your daughter’s hair, braid and fluorocarbon just can’t match that performance.
Practically, this means that a knot that holds in one line type may not hold well - or at all - in another.
And when you mix line types, which is common when we’re talking about leaders, you need to be pretty choosy about the knot that binds two different materials.
Always choose a knot that works in the line types you’re connecting.
How different are the diameters of the two lines?
When you tie two lines of the same diameter, knots tend to work pretty well. But when those diameters vary greatly, otherwise strong knots can fail.
That’s because the larger line can’t always create enough bite with the smaller one it’s paired with, though there are knots that are superior to others in this respect.
Now, you might think the answer is just to pair two equal diameter lines (or lines that are pretty close), and that’s typically easy when you’re talking about mono to fluoro connections.
But when you’re using braided mainline, that’s not going to happen, and you need a connection that can handle that difference in size without letting go.
Be careful about braid to mono/fluoro connections and choose a knot that can handle different line diameters.
Three Knots for Line-to-Line Connections
The FG Knot - Ideal for Trolling and Casting - Braided Mainline to Fluoro or Mono Leader
The FG Knot is a favorite of saltwater anglers who chase pelagic species, and it’s the go-to knot of pros and weekend fishermen alike.
Why do they like the FG knot so much?
- Strength - The FG knot is ridiculously strong, reaching the almost impossible 100%+ threshold. In practice, that means that, when properly tied, this knot will be stronger than your line itself!
- Versatile - It will hold braid to fluorocarbon or mono leader and really isn’t affected by line diameter. That’s a big, big deal, as most knots struggle when tied in lines of different thicknesses.
- Castable - While long, the FG knot doesn’t create a tag to bang against your guides, and most anglers find that it casts pretty well.
Those are simply huge advantages, and when you add to that the FG knot doesn’t require a bobbin to tie, you can easily see why it’s so popular.
Unfortunately, it’s not an easy knot to tie well, and it’s as slow as they come.
- Start by leaning your rod away from you to create tension on your braided main line.
- Hold the tag end of the braid in your mouth.
- Cross the braid with your fluoro leader from left to right.
- Pass the tag end of the fluoro back toward your rod and around the braid for one loop.
- Pull the fluoro tight and parallel to your braid.
- Repeat this process on the opposite side of the connection, toward you.
- Repeat this process back toward your rod.
- Do this again and again, for a total of 20 to 25 passes. Make sure that you pull your fluoro tight and straight each time. Make sure, too, that each coil is tight and stacked above the previous one--never crossing or bunching.
- With the tag end of the braid, loop both lines and pass the tag end back through the loop.
- Repeat this hitch knot up to 3 more times.
- Trim the tag end of the braid.
The J Knot - Ideal for Leader to Tippet
The J Knot is the darling of fly anglers the world over, and there’s simply no better connection you can make between fly leader and tippet.
What’s so special about the J knot?
- Strength - The J knot will regularly deliver as much as 83% of your line’s rated test strength, which is very strong by any standard. That number climbs with monofilament, the most common material for fly leader and tippet, and it’s reputed to reach as much as 100%!
- Easy - This knot is easy to learn and hard to get wrong. That matters a lot because any knot is only as good as you make it.
- Fast - Once you’ve learned the J knot, you can tie it in seconds, getting you back in the action quickly.
- Start with both lines facing in opposite directions and tie a simple overhand.
- Pass the right (as opposed to the left) lines behind and through the overhand knot.
- Again, pass the right lines behind and through the overhand knot.
- Wet your knot and cinch it down.
The Double Uni - Ideal for Joining Any Line to Any Line
The Double Uni is a great knot for connecting lines of different materials and diameters, and it’s popular in both fresh- and saltwater applications. While not great for casting, most anglers find that their leader lengths allow them to keep this knot out of their guides.
Why do people like the Double Uni?
- Strong - The Double Uni is very strong, especially when subjected to sudden force in a fight. As knot gurus will attest, “The strength of the uni-knot isn't diminished when the line is pulled with a jerk, rather than with steady pressure. Some knots, which test at more than 90 percent on a steady pull, will break at 50 or 60 percent if subjected to severe and sudden jolts--such as might be administered by a big fish surging boatside.”
- Fast-ish - There are faster knots you can use for a connection, but not faster, stronger knots! And once you get used to it, it only takes 10-15 seconds to tie.
- Easy - The Double Uni is an easy knot to learn to tie.
- Versatile - This knot will hold in braid, fluoro, and monofilament, and it’s pretty forgiving of different diameters.
The downside of the Double Uni is that it doesn’t cast particularly well, and it will bang through your guides, reducing casting distance and possibly compromising the knot over time.
Keep your leader short and the knot out of your guides.
- Start with both lines side by side.
- Loop the tag end of one around both lines, repeating 5 to 6 times. You’re essentially duplicating a standard Uni, but rather than doubling the main line, you’re wrapping the two lines you wish to join. Don’t tighten it down!
- Loop the other tag end around both lines, repeating 5 to 6 times. Don’t tighten it down!
- Wet your knots and carefully cinch them down.
There are advantages and disadvantages to every knot, and there are situations in which they all shine.
If you need a smooth casting, super-strong connection, and you don’t care how long it takes to tie, the FG is worthy of its unmentionable name. But the Double Uni is much, much faster, and with short leaders, it works really well.
Neither is a good idea for joining leader to tippet (or tippet to tippet), and the J knot is probably the way to go.
Select the right knot for your lines and situation, and you’ll be amazed at the results.