For the ritual proceeding, you first have to set up the sacred site. Above, the image of sacred site for Shinto ritual. Normally, sacred bamboos are set up at corners. Sacred rope
Bamboos are used for this purpose. I visited to Inaba Kōjinsai in Okayama (South-West Japan) in December 2015. There is little shrine for the local ancestral god, named Kōjin in high mountain. You have only 14 families (if my memory is correct) in the village.
I had a chance to observe from the preparation of this festival, thank to the professional kagura group, Jinkōsha 神光社.
Inhabitants of village are divided into two groups: female groupe and male one.
Principal task of male groupe is construction of stage. They had already prepared the bedding of the scene the day before.
The stage decoration of Bitchū kagura was particular.
After cutting down bamboos, two men are attaching the decoration (round rice cake).
The day was mid December, it was sunny but really cold. They burn big fire nearby to make them warm at the same time to burn trashes. In this picture, you see that it was very smoky.
After putting decoration, the bamboo is ready to set up. The longer of bamboo is over 3m.
They bind bamboos into four posts of stage.
There are already thick rope surrounds between posts.
Many gohei (sacred object with zig-zag paper) are put in. (I think this rope represents their ancestral gods (shape of snake), but I have to verify.)
These bamboos are called as imidake 忌竹. Sacred bamboos are tied by thin rope with gohei. Now stage is ready as sacred site for ritual.