The 24th fret is made from a brass plate attached to the end of the fretboard. It is the same size and shape as the other frets.
Have you ever noticed the weak tone of the neck pickups in 24 fret guitars? Here is the only standard guitar you can get, for any money, that has the pickup placed in the best harmonic node, and you still get 24 frets. The pickup is mounted as close as possible to the 24th fret - there is no bezel and no superfluous fingerboard wood. In fact the pickup is the same position it would occupy in a 22 fret guitar.