Kong-Ming Lock is an intelligence toy based on the principle of traditional Chinese mortise and tenon joint technology. It requires a bit of thought whether being dismantled and reassembled. The lock is shaped like the letter X which symbolizes the unknown. The painstaking process the Investigation Bureau uses to discover the truth in an investigation is similar to that required to figure out the value of X in an equation. Moreover, Kong-Ming Lock is placed over a pond in reference to the Chinese phrase shui luo shi chu (";When the water recedes, the rock surfaces.";), which means truth will ultimately be revealed.