A building installation reads like a tree: supply → meter → main board → final circuits. Learn the symbols for switch, socket, lamp, MCB, RCD and earth, then practise translating a floor plan into a wiring schedule: how many circuits, what breaker sizes, what cable runs. The manual's rule of thumb for a small Cambodian home: lighting 6 A / 1.5 mm², sockets 16 A / 2.5 mm², air-con 20 A / 2.5 mm² dedicated.