Hi!
This is a proposition for modelising the fingerboard of a violin!
First, you will use “Surface by section”, with the section profil curbs closed of the fingerboard.
For example, 3 closed curbs.
In yellow, you have the 3 curbs.
Then, you have the first step of the fingerboard.
But as we know, the upper part of the violin fingerboard has like if another little volume enters in the one we create. Sorry, i’m french, i hope it’s easy to understand! 
I hope we can see this on this picture, that shows in color pink the curbs of the upper part of the fingerboard.
So now, what we should do, is using the yellow curbs here, and, with “Patch” command, making another surface.
Then, once the surface is just created as we said with command “patch”, after, with in french, “décaler surface” command, as i show the command here, we will create a closed polysurface of this.
Here we have the “closed polysurface”.
And then, after a substraction boolean, between the fingerboard, and the little volume we created, we have the fingerboard of the violin!