Line to Line Knots

Learning how to tie fishing line joining knots is about more than simply knowing how to tie fishing line to leaders. Mastering a variety of line joining knots is a must for aspiring anglers, as different knots have vastly different uses. Learn more in this section.


Learning how to join fishing lines of different material, length and weight is a vital part of fly fishing.  Line joining knots tend to be popular fly fishing knots as well as critical in situations (like when you have a reliable rig on 15-pound test line and you want to attach it to the 20-pound test line on your reel without having to retie the whole rig). The below knots are tested and reliable for joining two pieces of fishing line.

The below knots are tested and reliable for joining two pieces of fishing line.


Triple Surgeon’s Knot

When first learning how to tie a fishing knot, most beginners are introduced to the simple surgeon’s knot. After all, it’s the one knot most beginners tend to know intuitively. In short, if you can tie an overhand knot, you can tie a surgeon’s knot, simply by making one more twist with the tag end. This simplicity is why the surgeon’s knot is one of the most popular line to line knots whatever your level of experience. Used in fly fishing most often for attaching the leader to the tippet, not only is this knot easy to tie, it also happens to be one of the strongest line to line knots you can use. The number of twists you make in the knot determines what type of surgeon’s knot it is. Two twists around is a surgeon’s knot (aka double surgeon’s knot), while three twists around is a triple surgeon’s knot.

This knot makes it easy to join two lines, but one line must be short enough to thread the end through the formed overhand loop. As with other lines, use a lot of overlapping line so that you can pull on all four ends to make it properly tight. Work with both lines together as you tie this, and make sure both loops are the same size to assure a strong knot.


A double uni knot is two uni knots tied back to back, then placed together to form a strong connection. For maximum safety, line joining knots such as the double unit should leave plenty of line at the end of the knot on each piece of line you're joining. The ends help pull the two knots into one. This line joining knot is great for attaching leader to your main line and works whether the lines are the same (braid to monofilament, or braid to fluorocarbon leader).

This is how you tie a double uni knot, you need to tie a uni knot with each of the two lines, with the knots facing opposite directions as follows:

  1. Lay your main line and your leader or secondary line out in front of you so that they overlap for a good distance, start with at least a foot of overlap until you know how much you need
  2. Form a loop in the left-hand portion of the overlap that goes clockwise. You should use the line that terminates to your left for this
  3. Pass that line around the other line and through the loop five times (see uni knot above). Snug the knot up, but don’t pull it tight
  4. With the line to your right, form a loop that goes counter clockwise
  5. Pass that line around the other line and twist it through the loop five times. If you are using a larger diameter leader you might only need three wraps
  6. Snug that knot up, but don’t pull it tight
  7. Lubricate the two lines between the two knots with saliva. Grasp both lines and pull them away from each other. The knots should slide together and pull tight
  8. Trim each tag closely. The finished knot should resemble a barrel.


Albright knots are popular fly line knots used for tying together two lines of unequal weight. In fly fishing, line to line knots of this type are routinely recommended for attaching the backing line (usually attached to the reel with an arbor knot – one of the most popular line to reel knots among fly anglers) to the main fly line. This knot is also extremely useful in situations when you wish to tie a 15-pound test line on your rig to the 20-pound test line you currently have on your reel spool.

  1. Fold the leader back to form a loop, and pass the main line through the loop
  2. Wrap the main line around itself and the loop 10 times
  3. Pass the tag of the main line back through the loop
  4. Start to close the knot with light pressure on both the tag and standing portions of the main line AND the tag of the leader
  5. As the line tightens drop the tag of the leader and the tag of the main line and pull it completely tight with pressure of the line against the leader
  6. Trim closely.


A blood knot (or barrel knot) is two back to back clinch knots. Because it is capable of maintaining a high portion of the line's inherent strength when used for joining sections of monofilament nylon line of similar weight, it is considered one of the strongest line to line knots. Other line to line knots used for this purpose can cause a substantial loss of strength. The principal drawback to the blood knot is the dexterity required to tie it. In fly fishing, this knot serves to connect a leader of gradually decreasing diameter to the tippet and is an alternative for using the double surgeon’s knot.

  1. Overlap the two lines
  2. Wrap your first line around the other line about 5 times, then take the tag end back towards the center and tuck it between the lines
  3. Repeat this process on the other side, wrapping the second line around the first and bring the tag end back to the center and tucking it between the lines. A this point both tag ends should be in the center, facing opposite directions
  4. Moisten the lines and tighten the wraps by pulling on the long ends of the line

Now that you are familiar with line joining knot tying. Learn how to tie other fishing knots and rigs