Luban ruler is a widely popular construction tools in ancient China. Used mainly to measure the size of residential doors and furniture. In ancient times, people think that the size determined by Luban ruler will shine auspicious gateway and will bring good fortune to the family.All objects resonate to a particular vibration depending on their dimensions, this can bring good luck and benevolence or misfortune and ill health. The energies that most strongly effect you are that of objects which are important to you or that you spend a great deal of time immersed in e.g., your desk, bed, office/arm chair.One of the most important object to measure is the front door, as this is the particular quality of Ch’i (energy) that is being invited in to your home or workplace.Use the fengshui ruler to attract good luck and stay away from bad luck