If you regularly hunt for buying both new and used acoustic or electric guitars, carrying a tiny string action gauge (often called a Fritz Ruler) in your wallet can save you from a costly buying mistake.
Why Every Guitar or Bass Player Needs a Fritz Ruler
When evaluating a used guitar, aesthetic wear is easy to spot—but playability issues aren’t always visible to the naked eye. High action makes a guitar painful and difficult to fret, while action that is too low causes persistent fret buzz.
Measuring the string height above the frets gives you immediate data:
Action Check: Slide the gauge onto the 12th fret to check the distance between the top of the fret wire and the bottom of the string. The Fritz Ruler is set up to do this for acoustic guitar, electric guitar, and bass.
Also, just use the Fritz Ruler to assess the thickest string and the thinnest string.
Target Measurements: The Fritz Ruler helps you estimate string action at the 12th fret (high or low) before you buy a used acoustic guitar, electric guitar, or bass.
String action at the 12th fret for all 3 instruments is debatable depending upon the musician. But here are some guidelines.
| Instrument | 6th String | 1st String |
| Electric Guitar | 1.5 – 2.0 mm | 1.0 – 1.5 mm |
| Acoustic Guitar | 2.0 – 2.5 mm | 1.5 – 2.0 mm |
| Bass Guitar | 2.0 – 2.5 mm | 1.5 – 2.0 mm |
Spotting Unfixable Problems: If an acoustic guitar has high action and the bridge saddle is already shaved down flat, the neck likely needs a costly neck reset. Catching this on the spot protects your wallet before you hand over cash.
Fritz Ruler to Buy a Guitar and String Action Ruler to Setup Your Guitar
Fritz Ruler
Just buy a Fritz Ruler on Amazon (currently $5.25) and carry it in your wallet. It’s shaped like a business card. Use it to assess whether a guitar or bass has “high” or “low” action. Or if the action is perfect already.
String Action Ruler for Precise Acoustic, Electric, and Bass Guitar Setups
These are sold all over Amazon and elsewhere.
Now that I string my own acoustic guitars, I am learning the importance of the String Action Ruler. I don’t need it to buy the new or used guitar/bass. But I need the String Action Ruler to measure “action” or string height at the 12th fret BEFORE I string my guitar.
- Before. Next time I will measure string height for thickest and thinnest string before I remove the strings. Why??? Acoustic example. Measure string height at the beginning of your guitar setup. If the action is too HIGH at 12th fret, the guitar is “telling” you that you will need to lower the saddle by sanding it or perhaps lower the strings at the nut. Most likely you need a saddle adjustment at the bridge.
- After. So you removed the old strings. You already know the action is high from your BEFORE measurement, so you lower the saddle a bit by sanding it down (that’s a process). You install the strings and measure the 12th fret action for height.
- The Logic. The Before and After string measurements give you solid numbers for knowing that you lowered your string action adequately. This whole argument could be how you raised the action of your strings. The same logic applies if you are raising the action.
I happen to like the Sunlego version since it has its own leatherette case so I don’t cut myself on its sharp edges.
Advanced Beginner Guitarists Own a Fritz Ruler and a String Action Ruler
Yes, we do.
The Fritz Ruler is your $5 insurance policy against buying an unplayable guitar with high action.
The String Setup Ruler is guitarists best tool for doing good guitar and bass setups.