There are a number of You Tube videos that will show you how this is done. Notched Straight Edge.
Hellfire Sawfish Guitar Notched Straight Edge Gibson 24.75", PRS 25", Fend 25.5"
Ragyzity Notched Straight Edge Guitar Luthiers Tool, 24.75" Notched Fret Board
Guitar Neck Notched Straight Edge Luthier Tool Fret Leveling Repairing Ruler UK
Guitar Neck Notched Straight Edge Luthier Tool UK Fret Leveling Repairing Ruler
Guitar Neck Notched Straight Edge Luthier Tool Fret Leveling Repairing Ruler
