top of page
Universal Notched Straight Edge | GMC Luthier Tools



The guitar notched straight edge checks the neck straightness & fretboard flatness independent of the frets.

Our Notched Edge Product Range includes 4 sizes of tool.

Luthier guitar repair tools UK | Notched staright edge options


The unique design of the notch spacing allows the tool to be used on an infinite number of guitar scales within the range quoted.

For example on the 24"-27" option, any scale length that falls between 24” and 27” (610mm-686mm) will be catered for. This includes over 20 popular scales including Gibson, Fender, PRS, Gretsch and the following:  24", 24.5", 24.5625", 24.625", 24.75", 24.84", 24.9", 25.0", 25.34", 25.4", 25.5", 26", 26.25", 26.5", 27", 630mm, 635mm, 640mm, 645mm, 650mm, 660mm & 670mm. Multiscale guitars can also be checked.


The tool has 18 notches on each side. The design of the tool is based on only checking the length of the fretboard that is capable of being deflected. The very highest frets are omitted as these are past the heel/neck join and won't be affected by truss rod adjustment or string tension.


The positioning on the neck will vary depending on the scale of the instrument. A double dot mark for position reference is provided on the tool. The dots are positioned at the 12th notch on the tool.

For shorter scales, the tool is used with the dots placed at the 11th fret on the guitar and for longer scales the dots are placed at the 13th fret. The 1st notch on each tool is larger than the rest in order to bridge over the nut when the tool is being used on shorter scale instruments.


A removable steady prevents the tool from toppling over, allowing it to remain positioned on the neck during setup and adjustments. Free-standing use provides easy observation of changes to neck when adjusting the truss rod. The steady can be used with or without strings fitted as the height is adjustable with reference to the straight edge.

To adjust the height of the steady, place the tool on the guitar and slacken the screw. The steady will find its own position on the fret top and the screw can be re-tightened.

Luthier guitar repair tools UK | Notched straight edge for acoustic guitar
Luthier guitar repair tools | Notched straight edge accuracy


The notched edges are all individually made from 3mm thick stainless steel and are 100% inspected for accuracy. The straight edges are milled in-house using specialist carbide tooling. The finished edges have a polished surface to within a total tolerance of 0.035mm (0.0015") over the tools length. The accuracy is checked on a calibrated (grade 000) precision granite inspection table - (table flatness quality inspection report 1.5 microns). Linishing is a hand finishing/polishing operation requiring attention to detail and serves as a 100% check of the milled straightness. All edges are dressed and sharp corners are de-burred and rounded over.


Combining 1) & 3)  will provide a scale range of 24" to 34" (610-864mm) - including a precision straight edge.

Combining 2) & 4) will provide a scale range of  24" to 38" (610-965mm).


The tool sizes are as follows:

30"- 38"  580mm x 50mm.

27"- 34"  515mm x 45mm.

24"- 30"  460mm x 40mm.

24"- 27"  410mm x 35mm.

Luthier guitar repair tools | Dual notched straight edge combination

24" to 38" Combination


GMC Luthier Tools Fret Levelling Tools and Abrasive Products feature a purpose designed fret levelling tool that utilises 25mm wide standard abrasive roll.


The tool comprises of a shaped hardwood handle made from black walnut and a stainless steel precision formed fret levelling tool/abrasive holder. The tool is manufactured in our workshop using precision die tooling. The manufacturing process includes linishing of the levelling face and flatness is guaranteed through 100% inspection of the tool.

Fret levelling tool UK | Precision made
Fret levelling tool UK | uses 25mm wide abrasive roll
8" Fret Levelling Tool
Fret levelling tool | with spare abrasive


The guitar neck should be set straight before levelling the frets. A notched straight edge will reference the fretboard and help to maintain uniformity of the frets for levelling.


The fretboard should be completely masked especially if the guitar has a natural /open grain or vintage finish. Any controls hardware and pickups should be protected from dust also.


The tool is supplied with emery abrasive. Emery has excellent abrasive properties and is designed for high precision and smooth surface finish. Dependent on fret wear, the abrasive included is sufficient for 4-6 fretting jobs, however as the emery becomes smoother it can be retained for lighter/polishing work.

Medium, fine & polishing grades are supplied with the fret leveller.

The starting fret levelling abrasive grade will be dependent on the degree of fret wear.


The abrasive is inserted through the tab slots and pulled taut at each end of the tool. The handle is then located onto the levelling tool and the allen screws tightened. A combination of tool pressure and the tab slot design keeps the abrasive in place without requirement for adhesive backed abrasive. The advantage of this is that 25mm standard abrasive roll can be utilised.

After levelling, the frets should be rounded over to reduce the flat areas of the crown. This is essential for good intonation. Our Fret Crowning Tool provides a solution for this and is suitable for most sizes of fret wire.


The tool is also useful for detail sanding/flat sanding of wood by incorporating a suitable abrasive.

(Emery supplied with the tool is not suitable for use on wood).

Fret levelling tool | can also be used for detail sanding

Detail Sanding of Fretboard


Fret levelling tool | can also be used for rasp sanding

Rasp Sanding of Guitar Neck

bottom of page