What is "kusari-fundo"

Kusari-fundo (鎖分銅) is a hand held weapon used in feudal Japan, consisting of a length of chain (kusari) with a weight (fundo) attached to each end of the chain. Various sizes and shapes of chain and weight were used as there was no set rule on the construction of these weapons. Other popular names are manrikigusari (萬力鏈) ("ten thousand power chain") or just manriki.