mono rig line escape


For those of us who prefer a mono rig over fly line for tight line (euro) techniques, line pull-through (escape) is a reality. Line pull-through occurs when the┬ámonofilament line pulls-through in between the fly reel’s spool and frame and will impede the drag / retrieve system of the reel. As some of us have learned the hard way, this can occur on hook-set or during the fight and can result in lost fish or even a damaged rod. While there are certainly tips on how to alleviate mono rig line pull-through, this post describes a solution that can fix pull-through permanently.


How does line pull-through occur

Line pull-through occurs when thinner mono line slips through the gap between a reel frame arm and the spool arm groove (see photo below).

why mono rigs pull through a fly reel

While on the surface this may seem like a problem with the fly reel, the gap is actually a known variance in reel design and is engineered with traditional fly lines in mind. Since traditional fly lines are much thicker than most mono used in tight-line rigs, the gap is small enough to keep traditional fly line from escaping, but not small enough for the mono. As a result, mono line can pull-through the gap between the frame arm and spool groove.


How to fix line pull-through for good

The approach presented here for fixing line pull-through is simple; use UV resin to build-up a shim on the frame arm and minimize the gap between the reel frame arm and spool groove. That’s right, just close up that gap as much as possible with UV resin and it should be good to go.

For this fix, the following tools are need:

  • UV resin that cures with a hard finish. I prefer the Thick Hard formula from Solarez, but others should work too. A thin resin can also be used, but may require multiple coats to build-up a large enough shim between the frame arm and spool groove.
  • A UV cure light.
  • Very fine sandpaper or a flat file that can be used to sand down the UV shim if it’s too thick.
  • The fly reel (obviously) and some monofilament line that’ll be used in the rig.

tools to fix mono pull-through

Step 1: Identify where on the frame arm to build the shim

To identify exactly where the shim needs go, unscrew your fly reel’s spool release and look very closely at how the frame arm fits into the groove on the spool. In most cases the UV shim will need to go on the very outside edge of the frame arm that fits into the spool groove. Also visually note how big the shim needs to be. In my experience it’s only necessary to build a shim 1mm or less, but will vary from reel to reel.


Step 2: Build the UV shim

Run a thin line of UV resin along the edge of the frame arm. This doesn’t need to be “pretty” as it’ll be hidden, but you want to focus on ensuring the shim is in the right place (outside edge of the frame arm most likely). If you make a mistake, just wipe the resin off and try again. Once you are happy with the shim, cure it with the UV light.

build UV resin shim


Step 3: Test the shim

Screw the spool back into the reel, and test it out.

In order to test the shim first try the retrieve on the reel and ensure the shim isn’t rubbing on the spool. If the shim is rubbing you will feel it catch on retrieve and will need thin the shim down a bit. To thin the shim you can either scratch all the (cured) UV resin shim off with your finger nail and rebuild the shim from scratch, or you can use fine sandpaper or a file to carefully sand the shim down a tiny bit.

sand UV resin shim

Once the reel retrieves nice and smooth, test that the shim is thick enough to prevent line pull-though.

To do this screw the spool back into the frame and try to force the mono line though the gap in the frame arm and spool groove from between the spool and frame arm. This is easily accomplished by running a piece of mono between the spool and the frame arm and bend it slightly into the frame arm groove on the spool. If the shim is proper thickness it shouldn’t be easy for the mono to escape up between the shim you made. If you can still easily get the mono line up through the gap, repeat steps 2 – 3 again to build up the shim a bit more until the line doesn’t easily pull through the shim.

Step 4: Repeat for remaining frame arms

Repeat steps 2 – 3 for the remaining frame arms, one by one, until they are all proper thickness. Note that you can build up and test all the frame arms at once, but it becomes more difficult to pin-point exactly which shim is rubbing if any of them are too thick.

complete UV resin shims


Maintenance & Care

While many UV resins on the market today are durable and should hold up well, the cured resin can scape off when the spool is removed and the shims are exposed. To get the maximum life from your UV shims, take care not to scratch / rub them any time the spool is removed and the frame arms are not protected by the spool. For reference, I’ve been using my UV shims for the better part of 2 years on my dedicated (no spool swapping) euro nymphing reels.



  • Q: Will this void my reel warranty?
  • A: Given most UV resins I’ve worked with will scratch right off with your fingernail, I suspect it shouldn’t. However if you are worried you can contact you reel manufacturer to understand what qualifies for a warranty void.