Tom (not his real name), a guitar tech with another company, came into the shop carrying a fretless bass. “I installed a new nut and followed all the directions to the letter but this thing is buzzing on open strings,” he said.

Inspecting the new nut, I noticed that he’d filed the slots right down to the fretboard. “Is that how Google and YouTube told you to do it?”, I asked. “That’s how everyone says to do it”, he replied.

As I write this article, most of the fretless “Gurus” are advising techs to cut nut slots down to the level of the fretboard where it meets the nut. Here’s a quote from a well-known and respected tech in the UK..

And so to fretless. If we follow this logic through, we could slot that nut until the strings touched the fretboard. The fingerboard is, after all, the equivalent of the fret-plane in this case. The string height setup will then be done at the bridge and some relief can be dialled into the neck if needed.

– Haze Guitars July 2022

The apparent reasoning is that two neighboring frets should be at the same height, allowing the natural climb of the strings as they progress to the saddle to provide the necessary clearance. Your fretboard represents your frets (zero fret) on a fretless guitar or bass. Ergo your nut slots should meet the fretboard at its level – so their logic goes.

Stop. Think. Do you see the flaw in this reasoning? Can you see why many of these gurus provide a “cheat” by adding, “But I allow several thousands of clearance, ‘just to be safe'”?

If you haven’t figured it out yet, here’s a clue – they’re comparing the area where the nut meets the fretboard to a zero fret. But frets must be crowned to prevent buzz. the crown of a fret provides the needed clearance so the strings make no contact as they leave the top of each fret.

Your nut is basically a fret when a string is played open. But where’s the crown? Where’s the “fall-away”? In short, “It ain’t there!” And that’s why your nut slots must be high enough for the strings to clear the fretboard where it meets the nut.

But how much clearance and how will we measure it?

If you had frets and wanted a 0.020″ clearance over that first fret, you would likely need about 0.015″ clearance where the fretboard meets the nut. At least, that seems like a good starting point. Next time I get my hands on a fretless, I’ll take some measurements and do some testing and add to this article.

Tom wasn’t too happy to hear that he’d have to scrap that new nut and start over, but at least it solved the “puzzle” for him!