Cylindrical unit, one of four which, when connected, channel lightning from the countless rods above the city of Atlantis back into the ocean. The rods are connected to a sophisticated Ancient terminal, and do not move without a command code.
If Zero Point Modules do not have sufficient power to activate the massive shield the lightning rods can separate to direct the raw energy through protected corridors and into the power generators. This energy can eventually be used to energize the shield.
The Ancient equivalent of 0-3-1-5-4-7, inserted into a rotating device, will separate the grounding rod (the lower half dropping away and rotating 90 degrees counter-clockwise) to utilize lightning power.
The Storm - Sheppard, Weir and McKay disable all but one of the grounding rods before a Genii strike force destroys the controls to the last one.
The Eye - McKay manages to reroute controls to release the grounding rod, allowing the city to channel the electricity of the storm.