在上盖中部也制有一圆孔，圆孔穿过底座上端和底座之间螺旋固定连接。

The middle part of the upper cover is provided with a round hole which passes through the upper end of the base and is spirally and fixedly connected with the base.

youdao

在上盖中部也制有一圆孔，圆孔穿过底座上端和底座之间螺旋固定连接。

The middle part of the upper cover is provided with a round hole which passes through the upper end of the base and is spirally and fixedly connected with the base.

youdao