Over in words from Classical mythology, Dr bill offers Tholos
The post includes this sentence; corbelling in this case means making roof of successively smaller
overhanging circles until a capstone can be applied.

What else would corbelling mean? i know sometimes it can be used to make a bee hive roof, but it can also used to describe an outward projection, bricks that have been corbelled out, to create a shelf for a window box, or an ornate cornice for a roof.

but inward or outward, corbelling is a change in dimension, by layering..
       
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my other obsession