The next job is to reduce the thickness of the front and back. Both pieces are between 5mm-6mm and quite uneven. The front needs to be initially reduced to around 4mm and the back reduced to about 3mm. This is done with the jackplane fitted with a toothed blade. Using a toothed blade reduces grain tear-out. What will be the outside surface of the top is first reduced to a uniform surface and then the thicknessing is carried out to the reverse side.

Spot the join!
Part 3 - Thicknessing and Surfacing
Plane toothmarks are removed and the thickness further reduced with a cabinet scraper. This is a thin piece of metal which has a burred edge (like a tiny continuous hook) which produces a really smooth, almost burnished, finish.  The final part of this process is to use finer and finer grades of sandpaper. Smooth as a baby’s bum! (But much more finishing to come...)
Same again for the back...
Making An Acoustic Guitar - Page 4