ammoon Fret Rocker Leverling Carbon Steel Guitar Luthier Tool No more guessing for the fret height and no more buzzing! The Fret Rocker can pinpoint those pesky high frets, and check the final height after you redressed or replaced them. 4-in-1 mini straightedge spans three frets, make it versatile for any fretted instrument, from basses to guitars to mandolins. The length of the sides makes it easy to check all of the frets right the way up the fingerboard.