Understring Fret Polisher

Understring Fret Polisher, Understring Fret Polisher
Understring Fret Polisher Item # 2219 In stock, ready to ship!
Kovax Tolecut Finish Repair System, Set of 6 Tolecut sheets
Set of 6 Tolecut sheets Item # 5729
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Understring Fret Polisher, Understring Fret Polisher with Kovax Tolecut Set
Understring Fret Polisher with Kovax Tolecut Set Item # 103248
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Understring Fret Polisher

Your fretwork just got faster. Get pinpoint control of fret polishing—without removing the strings. With instantly changeable grits this single tool is like a drawer full of files. 

Made of stainless steel, the Understring Fret Polisher has a concave fret-shaped groove like a traditional crowning file. This smooth groove makes it easy to attach adhesive-backed abrasives—making it a super fast fret polisher. And the special ultra-thin shape fits where traditional files can't. 

Any grit you need—instantly
Unlike a traditional file, you can easily change to the exact grit you need with the same tool. Just cut the grit you need to size with a Razor Knife and attach it to the groove. You can also use Double-stick Tape for regular abrasives. We put a different grit on each end for lightning fast changes. 

Our favorite abrasive to use is Kovax Tolecut. The ultra fine Tolecut removes scratches and polishes with little effort. And Tolecut lasts an incredibly long time: one sheet will give you approximately 72 uses!

The fastest way to polish
It's easy to use: simply raise the strings on both sides of the fret you are polishing with String Jacks, then work through abrasive grits for a mirror shine. The custom shape stays on the fret for incredible control. Abrasives and sandpapers conform to the shape of the fret as you use it.

Complete fretwork under the strings
Because you don't need to remove or replace the strings, you'll save time on every leveling job. It's the perfect follow up to the Fret Kisser when spot leveling a single fret. And with the Fretbar and Understring Fret Dressing Files you'll level, dress, and polish in record time. It's so fast we use it with the strings off too.


  • Durable stainless steel construction
  • Change grits in an instant
  • Fits all fret sizes
  • Works with the string on or off

Everything you need in one set
Start polishing right out of the box with the complete set. We include all of the grits you need to get a mirror shine.

Each set includes:

  • 1 Understring Fret Polisher
  • 2 String Jacks
  • 6 Tolecut sheets, 1 of each grit: 800, 1200, 1500, 2000, 2500, and 3000-grit

Polisher: 6" x 1/8" x 1/8" (152.40mm x 3.17mm x 3.17mm)
Each Tolecut abrasive sheet has 8 self-stick squares, 1-1/8" x 1-3/8" (29mm x 35mm)

Works on stainless frets, too!
All of our tools are suitable for use on stainless-steel fretwire*. Modern stainless-steel fretwire is known to be harder than the traditional nickel-silver blends, but our own shop experience indicates the wire does not cause premature wear of files or sandpapers.
*Excludes our original Fret Tang Nippers. We recommend our Deluxe Fret Tang Nippers for stainless-steel fretwire.
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Cancer and Reproductive Harm