Fly Line Backing Knot: Which Knot and How to Tie It

The two knots you need

Spooling a reel takes two joins. The first holds the backing to the reel's arbor (the central core of the spool). The second joins the backing to the back end of the fly line. Vail Valley Anglers recommends a simple arbor knot at the reel and a nail knot or Albright knot to the fly line, backed up with super glue or Loon UV Knot Sense. Fly Lords walks through the arbor and the Albright, so those are the two I describe in steps.

You may also see the third join, fly line to leader. That is the leader, not the backing, so I leave it for our fly rod setup guide.

Step one: the arbor knot (backing to reel)

Per Fly Lords:

1. Wrap the backing around the arbor and tie a simple overhand knot around the standing part, the long length that runs to your supply spool.
2. Tie a second overhand knot in the tag end, about 3 inches from the first.
3. Pull the standing backing. The first knot slides down onto the arbor and the second jams against it.
4. Trim the tag end next to the spool.

The logic is a knot that tightens as the backing is pulled. If a fish takes you all the way to the end, the knot is the last thing holding the whole connection, so it earns a moment of attention. Tie it snug, pull it firmly, and trim neatly. MidCurrent adds that backing should be wound on evenly and under tension so it does not bite into itself, which is the spooling guide's job, not the knot's.

Step two: the Albright knot (backing to fly line)

The Albright joins lines of different diameters, here a thin backing and a thick fly line. Fly Lords describes it like this:

1. Make a loop in the end of the fly line and pass about 10 to 12 inches of backing through it.
2. Hold the three sections between thumb and index finger, then wrap the backing over itself and both strands of the loop.
3. Make 8 to 10 tight wraps, then feed the tag end back through the loop, exiting on the same side it entered.
4. Hold both ends of the fly line, slide the wraps toward the end of the loop, pull the backing to tighten and trim the tag close to the knot.

Fly Lords says the Albright is good at sliding through the guides when a fish pulls you far enough to reach your backing.

The nail knot alternative

Vail Valley Anglers names the nail knot as the other common option. Fly Lords lists the nail knot for fly line to leader: you place a small tube or nail under the fly line and the butt of the leader, wrap the butt several times back toward the fly line, pass it through, then pull it tight. I have not opened a step-by-step page for the nail knot as a backing join, so if you choose it, follow the instructions for that knot from a source you trust.

Finish and check

Vail Valley Anglers backs up the fly line connection with super glue or Loon UV Knot Sense. That is a maker-level choice, and Fly Lords does not mention it, so decide for yourself: if you glue, use a small amount, keep the knot smooth, and let it set before you wind line over it.

Whichever knot you use, pull it hard before you reel anything on. Fly Lords advises a solid check before casting. Then check it again after a hard fish.

Splice or knot

MidCurrent says Dacron backing is hollow-braided, so a skilled person can splice it to form a loop or insert another line. A fly shop can do this, and shops also have machines that spool backing, line and leader tightly. If you are not confident with knots, ask them to spool your reel.

Which backing, and how much

The knot is only one decision. How much backing the reel takes is in our how much backing guide, and the backing page lists products with breaking strength, spool length and material. Before you tie anything, read the reel's capacity table, and remember Vail Valley Anglers' reminder that too much backing is usually a bigger problem than too little.

Fish don't read spec sheets. You should, and the capacity chart and the knot are the two places where a few minutes at the kitchen table pay off at the river.