石敢當 Ishigantou (or ishiganto) are another common feature in Okinawan neighborhoods. They are stone tablets, talismans to ward off evil spirits: 石 ishi means “rock,”敢 gan means “a challenge,” and 當 tou means “to strike/hit.” You will see them on every intersection; they keep bad spirits from entering homes near intersections and weaken their power (because evil spirits can only go in straight lines, they cannot turn).
It is a tradition that came from China a long time ago, and is prevalent all over the islands. Walking around just my neighborhood it is possible to see dozens. Some are handmade, some are plain, and some even have fancy designs; you can purchase many types at the DIY home center (like Cainz, Makeman, Sakamoto, etc). Just like shisa, this is another traditional way to protect the home.
There is even one on our laboratory door at university.