A barrel or cask is a hollow cylindrical container, traditionally made of wood staves and bound with iron hoops. Someone who makes such barrels is known as a cooper. Contemporary barrels are also made of aluminium and plastic. Barrels often have a convex shape, bulging at the middle. This constant bulge makes it relatively easy to roll a well-built wooden barrel on its side, changing directions with little friction. It also helps to distribute stress evenly in the material by making the contain… (More on Barrel)