Javelins believe it or not, are members of the rodent family.
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Initial javelins were made of wood until the mid-1950's. Dick Held improved javelin aerodynamics and durability by introducing aluminum javelins around that time (his brother, Bud, was the world-record holder for a time). Current javelins are made of steel, aluminum and/or carbon fiber.
wood and iron
The plural for for javelin is javelins.
A roof and a building