Double Uni Knot: Join Braid to Mono or Fluoro
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A double uni is 2 uni knots, 1 tied in each line, pulled together.
For braid to fluoro, use 8 to 10 turns on the braid side and 5 or 6 on the leader side. It takes 5 steps and no tension tricks, which is why it's the fast option on the water.
The tradeoff is bulk. The joint has 2 barrels of turns, so it's thicker than an FG knot. With a leader shorter than your rod, that rarely matters.
Spec card
Double uni knot
- Connects
- braid to fluoro or mono leader; mono to mono; fluoro to fluoro
- Line types
- any pairing of mono, fluoro and braid
- Turns
- braid side 8 to 10; mono or fluoro side 5 or 6fewer on leaders over 20 lb; see the table
- Overlap to start
- 6 to 8 in.
- Tightening order
- each knot snug first, then pull the standing lines
- Don't use for
- line to hook (use 1 uni); joints that must slide through the guides on every cast
The 5 steps
Overlap the 2 lines by 6 to 8 in. Lay them side by side with the tags pointing in opposite directions.
Step 1. Overlap the 2 lines by 6 to 8 in. Tap to enlarge. Tie a uni with the leader tag around the braid. Make 5 or 6 turns through the loop.
Step 2. Tie a uni with the leader tag around the braid. Tap to enlarge. Tie a uni with the braid tag around the leader. Make 8 to 10 turns through the loop.
Step 3. Tie a uni with the braid tag around the leader. Tap to enlarge. Snug each knot on its own. Pull each tag until its turns close into a neat barrel.
Step 4. Snug each knot on its own. Tap to enlarge. Pull the 2 standing lines apart. The knots slide together and lock. Trim both tags.
Step 5. Pull the 2 standing lines apart. Tap to enlarge.
Each knot in steps 2 and 3 is a full uni. If you can tie one uni, you can tie this. The only new parts are the overlap and the tightening order.
Practice it 5 times at home with 2 colors of line. Then you'll see which turns belong to which knot.
Hold the overlap in the middle while you tie the first uni. Your fingers keep the lines from separating. After step 2, the first knot holds the overlap for you.
How many turns on each side?
Our assumptions
- A turn: 1 pass of the tag through the uni loop, around both lines.
- Range: what published instructions give for each line class. Counts vary by source.
- Direction: braid gets more turns than mono or fluoro, because it's slick.
| Pairing | Braid side | Leader side |
|---|---|---|
| 10 to 20 lb braid + 8 to 12 lb fluoro | 8 to 10 | 6 |
| 20 to 30 lb braid + 15 to 20 lb fluoro | 8 to 10 | 5 or 6 |
| 40 to 50 lb braid + 25 lb fluoro or mono | 8 | 4 or 5 |
| Mono to mono, 6 to 15 lb | 6 (both sides) | 6 |
| Fluoro to fluoro, 6 to 15 lb | 5 or 6 (both sides) | 5 or 6 |
The leader side gets fewer turns as the leader gets thicker. Heavy fluoro is stiff, and 6 turns of 25 lb won't close neatly. The braid side stays at 8 or more because braid needs contact to grip.
For diameters, see the pairing table on our FG knot page. It lists braid and fluoro sizes from the maker charts. The same pairings work for a double uni.
Tightening order
The order changes how the knot seats. Follow it each time.
- Wet both knots. Friction heat curls fluoro and mono.
- Close the leader knot first. Pull its tag, then its standing line, until the barrel is firm.
- Close the braid knot. Pull the braid tag hard. Braid turns need a firm pull to bed down.
- Slide them together. Pull the 2 standing lines apart with steady force. The barrels should meet and touch.
- Trim. Leave about 1/8 in. on each tag.
If the knots won't meet in step 4, one barrel is too loose. Go back and close it harder. A gap between the 2 knots means the joint can twist and fray.
On heavy braid in grass or wood, some anglers step the leader up. A 30 lb fluorocarbon leader is about as thick as a double uni closes neatly by hand. Check the diameter against your braid first.
Double uni or FG?
| Question | Double uni | FG |
|---|---|---|
| Steps | 5 | 7 |
| Needs tension while tying | no | yes |
| Joint thickness | 2 barrels of turns | braid wraps only |
| Goes through guides often | bulkier | slimmer |
| Works mono to mono | yes | no |
Both are braid-to-leader knots. Neither page here makes strength claims. The difference is practical.
Pick the double uni when you're tying on the water, in wind, or with cold fingers.
Pick the FG when the joint passes the guides on every cast. That happens when the leader is longer than the rod. A 3 ft leader on a 7 ft rod keeps a double uni outside the tip on most casts.
Braid, fluoro and mono: what changes
| Pairing | Works? | Watch for |
|---|---|---|
| Braid to fluoro | yes | braid side needs 8 or more turns |
| Braid to mono | yes | mono stretches, so close the mono knot firmly |
| Mono to mono | yes | same turns on both sides |
| Fluoro to fluoro | yes | wet well, close slowly |
| Braid to braid | yes, with care | 8 to 10 turns on both sides |
Joining 2 lines of very different diameter is the weak spot. Thin braid on thick 30 lb mono can work, but the thick knot may not close well. For a big diameter gap, look at the Albright knot.
Where it fits on the water
- Spinning reel, 15 lb braid to 8 lb fluoro: finesse bass in 10 to 20 ft, on a light braid such as 15 lb SpiderWire Stealth. The double uni is quick to tie on the deck.
- Baitcaster, 30 lb braid to 15 lb fluoro: Texas rigs around docks. Keep the leader near 3 ft so the joint stays outside the guides.
- Topping up a spool with mono over old mono: a double uni joins 2 spools of the same line.
Leader length and retying
Every hook change shortens the leader. Plan the leader length around that.
A Palomar on a small hook uses about 6.5 in. per tie, from our Palomar calculator. Start with a 36 in. leader and stop at 18 in., and you get 2 reties. Start at 48 in. and you get 4.
Then the leader needs replacing, which means a new double uni. That's 6 to 8 in. of overlap from each line. Braid is the line you lose slowly. Over a season of retied leaders, the braid on the spool gets shorter by 6 to 8 in. each time.
Keep an eye on spool fill. When the braid sits well below the lip of the spool, casts get shorter. Our arbor knot page covers refilling.
Checking the joint
Look at it before the first cast. Then pull.
- Barrels touching: no gap between the 2 knots.
- Turns countable: 8 to 10 on the braid side, 5 or 6 on the leader side.
- Tags short: about 1/8 in., no longer.
- No curl: a kinked, curly leader near the knot means it got hot. Retie.
Pull steady with both lines wrapped around something firm, like a reel handle and a glove. Don't jerk it. If a barrel slides along its line, that side needs more turns or a harder close.
When to skip the double uni
- Long leaders through the guides. The 2 barrels tick the guides on every cast. Tie an FG.
- Line to hook. One uni does that job. See the uni knot.
- Big diameter gap. Very thin line to very thick line; consider an Albright.
Common Questions
Why does the braid side need more turns?
Braid is slick and thin. Mono and fluoro grip themselves better because they're softer and thicker.
Extra turns give braid more contact inside the barrel. That's why most instructions call for 8 to 10 braid turns against 5 or 6 on the leader. If the braid side slips, add 2 turns before changing knots.
Can you tie a double uni with 2 different line weights?
Yes. That's the usual case: 20 lb braid to 12 lb fluoro, for example. Tie each side with the turns that suit that line.
Very large gaps are harder. A thin line can cut into a thick knot that won't close fully. Berkley recommends the uni-to-uni for lines of similar diameter. For a big diameter gap, switch to an Albright.
How long should the tags be?
Overlap 6 to 8 in. at the start. That gives each tag enough length for 5 to 10 turns with room to hold.
After the knots meet, trim each tag to about 1/8 in. Long tags catch weeds and tick the guides.
Gear for this page
Seaguar Blue Label 100% Fluorocarbon Fishing Line leader, 30lbs, 25yds Break StrA 30 lb fluoro leader for the double uni.
SpiderWire Stealth Braided Fishing Line, 10lb, 125 yd, Moss Green, 1 Ct15 lb braid main line for a double uni to a leader.- Seaguar Fluorocarbon Leader 20lb Test 25 Meter CoilA 20 lb leader if you move up to the FG knot.
Rapala RSD-1 Line ScissorsCuts both tags short after the double uni.
Next knots
- Fishing knots by connectionthe full decision table
- Uni knotthe single knot inside the double uni
- FG knotthe slimmer braid-to-leader join
- Improved clinch knotleader to hook on mono or fluoro
- Knot tying toolsclippers and tools by job
- Fishing line for bassmono, fluoro, braid and copolymer by technique
Sources: published double uni instructions for steps and turn ranges. Diameter pairings from PowerPro and Seaguar charts (see the FG page). Method on our methodology page.. PowerPro knot guide and Berkley, "Fishing knots 101," for turns per side and the similar-diameter rule.