Marking the back outline

Time to mark the outline. I mark both the outline of the ribs, and the edge of the back which should be offset by 4 mm for a 4/4 cello. With the scale of this 3/4 cello (I am scaling all linear dimensions by 91.4 %) that comes to 3.6 mm. Luckily I have a washer of exactly the right dimension. In addition to those I also added enough wood for the button. Do not forget to do that!