Fasten a smooth brass button to a cork so that you can hold it firmly, and rub the button as hard as you can on a rough piece of wood.

将一个平滑的铜质按扣固定在软木塞上, 确保两个东西牢牢固定在一起, 然后竭尽全力地在一块粗糙的木头上摩擦。