Wikipedia
Fukiishi
( or "roofing stone") were a means of covering burial chambers and burial mounds during the kofun period of Japan . Stones collected from riverbeds were affixed to the slopes of raised kofun and other burial chambers. They are considered to have descended from forms used in Yayoi-period tumuli. They are common in the early and mid-Kofun periods, but most late Kofun-period tumuli do not have them.
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