Lu Ban ruler is a ruler used to measure and measure in the construction of Duong Trach (house) and Am Trach (grave), on the Lu Ban ruler has the usual geographical size and arcs to help determine good or bad intervals. bad, helping users know what size is good to use and what size is bad to avoid. Eastern people respect their beliefs, always have the concept of "abstinence is good", so in anything, they are carefully considered. From marrying and marrying, you also have to look at age, see the