Lots of answers arose. Some participants in the discussion could not picture the "silver pots on the posts", which made it difficult to speculate. I said, I've seen them, but don't remember where.
So I set out to find one and take a picture. I turned around at the first opportunity and came home and walked. It was all of 300 steps away down the road.
Here are the pictures. What is it? What is it for? If you post an answer in a comment, please tell us if it is a guess or from actual knowledge and experience.
This one is number 5.
Well, if anyone should still be wondering, here is an explanation from Hawaii.