Abstract: A construction of a panel includes at least one opening defined therein, a first and a second box are respectively disposed beside the opening of the panel, each of the first and second boxes has a hole defined therein and an extending live line and an extending ground line respectively extend from the first box and the second box and extend along sides defining the opening, one end of the extending live/ground line is in communication with the corresponding holes of the first and the second boxes. The extending live and extending ground lines are respectively and electrically connected to an electrical element disposed in the panel, which has two conductive plates extending therefrom, each of the conductive plates has an L-shaped plate extending transversely therefrom so as to receive the extending live/ground lines between the L-shaped plate and the conductive plate.