Onlay grafts are grafts which are laid on top of an area. Theoretically, this graft can be placed anywhere within the nose. Most often this graft serves to augment an area which is deficient in cartilage which would otherwise cause a depression.
When using an onlay graft it is important to make sure that the graft does not have sharp edges. A technique which is useful is called chamfering. A champfer is a technical term for a beveled edge. Often times slightly crushing the edge of the cartilage graft will prevent it from being seen externally.
Onlay grafts are in the category of grafts termed visible grafts. Grafts which are placed underneath the existing framework of the nose are called invisible grafts. Invisible grafts have less risk for visibility but may not be implemented in specific instances.
"The nose should fit the face"
A strong jawline would suggest a stronger nose.