Some granite fabricators will cut out a place underneath the granite for steel rods or plates that tie back into the island. This way it supports the granite without any corbels (knee knockers) underneath and they remain unseen unless you kneel down and look up.

It depends on the style of the home. Traditional and old world homes often feature corbels, while contemporary homes will look to hide the supports for a cleaner look. The corbels themselves rarely support any weight.