In order to get a 24 fret extension the neck must be Warmoth Pro construction. That means if the neck is a tiltback (Regal, Warmoth, Vortex, Arcade, e.g.) truss rod access will be at the headstock. If the neck is straight (all the Fender styles, e.g.) access will be at the heel, with an included side-adjust mechanism that allows adjustment of the truss rod without removing the neck.