Anyone who has ever been to school would have seen many blackboards big and small on which characters in different colors of chalk are written. The blackboard is a kind of cultural tool. It is usually made of wooden boards four to five cenlimeters thick in the shape of a rectangle. It is painted black on the surface with black paint. Underneath there is a groove for dust.

任何到过学校的人，总见过许多大大小小的，上面写着各种颜色粉笔字的黑板。黑板是一种常见的文化工具，它一般呈矩形，用本质夹板做成，厚四五厘米。它的正面涂上黑漆，下面还有一条积灰槽。

With the development of the educationaI cause, there has been an increasing development in cultural facilities and equipment. The varicty of blackboards is on the rise. There are glass-made blackboards, velvet blackboards made on the basis of the function of statics, magnetic black-boards made according to the function of magnetics, etc.

教育事业的发展，促进了文化用品的发展。黑板的品种不断增多，有玻璃黑板，有根据静电作用造出的绒布黑板，有根据磁性作用造成的磁性黑板

The blackboard is so mon and unattractive in our life, yet it has played an important role in our study, Our teachers have written equation after equation and solved countless problems on it. It is such a mon rectangular blackboard, but it is the golden key to the door of the treasure house of knowledge.

黑板在生活中是司空见惯的，然而却在我们的学习中起着重要作用。老师在黑板上写下一个又一个的方程，解决了无数难题。就这样一个普通的长方形黑板，可却是通往知识宝库的金钥匙。