Extinction means completeness, that is, nothing remains.
Luban ruler is also called door mirror, door mirror ruler, sky measuring ruler, curved ruler, Dinglan ruler, door mirror, door mirror ruler, curved ruler, nine-cun ruler, etc. Its ruler body consists of eight right-angled rulers. and a beam. In ancient Chinese architecture, wherever the length needs to be measured, such as palaces, temples, houses, mausoleums and other buildings, a telescopic door mirror - the "Luban ruler" must be installed. The Luban ruler is a commonly used calculation instrument in the woodworking industry and an important invention in ancient Chinese architecture. This kind of ruler consists of nine right-angled rulers and a cross beam. Each of the right-angled rulers is engraved with 45-degree divisions, and can be measured according to the dimensions marked on the Luban ruler.