Some theories on why the chain armor that knights used to wear was called mail include the idea that it was hammered together.

一些理论考证说，曾经穿在骑士身上的锁子甲之所以叫做mail(铠甲)，和它是被敲打而成有关。

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One display offers an exploded view of the armor's constituent elements, from shin guards and boots to chain-mail sleeves and the shoulder guards that rest against the warrior's back like folded wings.

WSJ: Dressed to Kill in Peacetime | Samurai! | Museum of Fine Arts, Boston | By Lee Lawrence