Bert. I'm sure others could do a better job of explaining, but, in their absence... In traditional design the neck stops at the body of the guitar and the fretboard extends over the top of the guitar and is glued directly to it. Therefore when the neck must be adjusted backward or forward to allow for curvature of the neck (necks generally tend to fold forward over time), there occurs a 'hinging' of the fretboard where it joins the body. In other words when the neck moves the part of the fretboard glued to the guitar top does not. Taylor's new design has an extension of the neck under almost all of the fretboard and this neck piece slots into the top of the guitar.