What is the purpose of the kamigoma?

I have a kamigoma for my beginner’s shamisen. What is its purpose? Is it for the sawari sound for the low thinner strings? I followed Kyle’s video for sawari and put some tape under the ichi no ito and the ichi no ito buzzes like a charm!

On a nagauta shamisen, only the ichi no Ito is supposed to rest on the wood. The kamigoma supports the other two, so that the sawari comes through for the ichi no Ito on every string, but the ni and san no Ito don’t buzz against the wood the same way.