Legend has it that Lu Ban, considered the ancestor of carpentry and revered as a saint, invented the Lu Ban ruler. There are various theories about the origins of the Lu Ban ruler, but it is known in Feng Shui for its application in measuring lengths in the design of buildings and grave sites.
Currently, the commonly used Lu Ban ruler is 43 cm long and divided into 8 equal segments:
| Segment | Meaning |
|---|---|
| Wealth | Associated with the Star of Shen Lang, which signifies Life Energy – Good |
| Illness | Associated with the Star of Pa Jun, which signifies Death – Bad |
| Separation | Associated with the Star of Wu Ku, which signifies Blessings – Good |
| Virtue | Associated with the Star of Ju Men, which signifies Protection – Good |
| Official | Associated with the Star of Wen Ku, which signifies Six Harms – Bad |
| Calamity | Associated with the Star of Lian Zhen, which signifies Five Ghosts – Bad |
| Harm | Associated with the Star of Lu Cun, which signifies Disasters – Bad |
| Support | Associated with the Star of Tuo Fu, which signifies Assistance – Good |
Measuring lengths in buildings or objects that fall into the Wealth, Separation, Virtue, and Support segments is considered favorable, while those falling into other segments are deemed unfavorable.
There is also a 52 cm version of the Lu Ban ruler, divided into 8 equal segments as follows:
| Segment | Meaning |
|---|---|
| Noble Person | Associated with Wood – Good |
| Peril | Associated with Earth – Bad |
| Natural Disaster | Associated with Earth – Bad |
| Heavenly Wealth | Associated with Water – Good |
| Human Wealth | Associated with Metal – Good |
| Loneliness | Associated with Fire – Bad |
| Heavenly Robbers | Associated with Fire – Bad |
| Prime Minister | Associated with Earth – Good |
You can use either of these rulers for measurement and calculation, or both if desired.
The scientific basis of the Lu Ban ruler is subject to various interpretations. Some theories suggest it is an extension of the Eight Trigrams and that its use follows the principles of the Eight Trigrams and the Five Elements. However, science indicates that even within the earth, there are vibrations with different frequencies, especially persistent negative vibrations. If the dimensions of a building or object align with certain wavelengths, it may cause resonance and reduce stability. The Lu Ban ruler may therefore be a product of accumulated experience in construction to avoid resonance or strong wave patterns, thus minimizing risks and extending the longevity of buildings and objects.