blackboard

He chalked out a design on the blackboard.

他用粉笔在黑板上勾划出一个图样。

She rubbed the exercises off the blackboard after class.

下课后她把习题从黑板上擦掉。

The teacher knocked on the blackboard to catch our attention.

老师敲了敲黑板以引起我们的注意。