People who aren’t intimate with violins don’t have to consider all of the things a maker has to. There are all sorts of details on a violin that have to be done in some intentional way. Not necessarily one way… I don’t mean that. I mean that when you have to do them, you find yourself wondering exactly which choice of the many you should make.
The cut off ends of the ribs at the corners are an example. There’s a definite thickness there; the c-bout rib feathers off to nothing on the inside of the joint (which is a miter, like on the corner of a picture frame), but the outer rib overlaps that and has about 1mm of thickness. You can cut the ends off to mimic the tip of the corner of the top and back (that’s the way that many people find natural, that’s often taught in violin making schools). Some makers in the past trimmed down the outer rib to form a sharp point; that’s logical, but fragile. Makers who taught themselves, and schools that put clamps on the ends of the rib when they glued the rib tips together, often bring both ribs up to the end full thickness, 2mm, with the joint in the center. If they were looking at good violins, they might have subsequently thinned both ribs so that the whole width of the end was 1mm. Some very obscure schools brought the inside, c-bout, rib out to the end, and feathered the outer one, so the (invisible) joint is at the outside of the end of the corner.
The corner in my drawing is the way that 17th century Cremonese makers did it: they cut the end of the (outer) exposed rib off square, so that it doesn’t match the end of the corners of the top and back. It doesn’t make a whole lot of visual sense, in context, but it’s the strongest way to make the tip, so that it doesn’t quickly wear. Guarneri del Gesu, with his sometimes very long corners backed up by blunt endings on the corner blocks that didn’t reach far enough out to give much support, often carried the outer rib out past the inner one a mm or two, by itself, and then finished it off square.
There’s lots to think about for just the end of a rib, and yet virtually everything you see on a violin has been similarly considered, calculated and designed to give a particular effect.