The quality appearance of a product, i.e. the feeling of quality the customer gets from a product, is highly dependent on the visual impression the product conveys to a customer when observing it. For the exterior of an automobile, the visual quality appearance is depending on the relations (split-lines) between all the parts, i.e. hoods, fenders, doors, etc. A car built with high precision gives a good quality impression.

The quality of the split-lines, i.e. the size of the gap, the flush, and parallelism, is, in turn, depending on the tolerances and the geometric variation in the individual parts, the way parts are located and assembled to each other, the position of the split-lines on the body and the geometry of the body.