Or, “Mother, the chevrons are locking!”

Considering it’s just a big, spinning wheel, there’s actually a surprising amount of ambiguity about exactly how the Milky Way version of the Stargate dials. The basics are obvious. There’s an inner ring, which rotates alternatively clockwise and counterclockwise to indicate specific symbols on it, each of which is represented by one of nine corresponding chevrons on the main ring of the device. The chevrons are numbered one through seven, proceeding clockwise, ending with seven at the top, and skipping the bottom two chevrons.¹In the subsequent television shows, we saw eight- and nine-chevron addresses. The nine-chevron address engaged each chevron in clockwise order, with the bottom-right chevron becoming chevron four and the normal chevron four being chevron six, and so on. The implication in “The Fifth Race,” the first episode where it was done, is that the first six symbols encode under the normal chevrons, while the additional seventh symbol encodes at the bottom right chevron (briefly seen on a computer screen), with chevron eight at the top, which is confirmed by comparing the visible symbols on the Atlantis stargate in the episodes “No Man’s Land” and “The Pegasus Project” with the published eight-symbol address for Earth.

So the question left is, exactly what position on the main ring indicates which symbol is being encoded or locked by a given chevron?