1 top three entrances in turn to the power supply to reach you here at the forefront (that is, can not pass through any switch, the surge protector if the switch with the exception of this is afraid of a switch error caused by the protection was withdrawn from the real role
2 lower grounding port in addition to ensure that a reliable grounding must be ensured at the same time and you install a surge of equipment (distribution boxes or distribution boxes). The grounding port at the lower end must be reliably connected to the shell of the equipment you are installing the surge (distribution box or cabinet) in addition to ensuring reliable grounding.
I hope this will help you