The Sanctuary F posts.

Center of The Sanctuary showing the position of the '7 Foot Ring
Post positions marked in red.

There are eight 'F' posts.
"The 7 Foot Ring".

The sole purpose of the 7 Foot Ring seems to be to act as markers for the next ring (the 10 foot 'E' ring).

The position of the G posts  is echoed by the posts placed between the 'corridors'.

G posts in green.

Center and middle of The Sanctuary.
How the F Posts act as position markers for the four 'corridors'.

When the post holes were excavated they were found to be "filled with distinctive brown mold without any relics". Nor were there any trace of cores in any of the holes.

Size of the post holes.
Average 30" deep (43"-24") 43 inches= 1 metre, 24 inches= 60 cm.
At the top, the hole size was  12"-18 "= about 40 cm.
The diameter at the bottom of the post 6" inches diameter = 15 cm.

Arrangement of posts.
As at Woodhenge, the F posts follow a pattern, or exhibit a symmetry based on 1 and 2.

The pattern here is 2, 1, 1, 2, 1, 1.

The F posts exhibit a symmetrical pattern based on 1 and 2.
This is also found at Woodhenge.

If this 2112 pattern is significant, it means that the position of the G posts were used as a guide for the placement of the F posts. But I can't help thinking that after the corridors post holes had been dug, and trees dragged into position, replacing the G posts would have been an awkward task.