在目前用来决定铅直线或水平线的工具总括起来可以分为三种类型。第一种是利用液体平面为基准的；第二种是利用重力线为基准的；第三种是利用水准器为基准的。过去由于工业上制造技术的限制使得第一种和第二种长期地 In the current tools used to determine the vertical line or horizontal line can be summed up in three types. The first is to use the liquid plane as a reference; the second is to use the gravity line as a reference; and the third is to use a level gauge as a reference. In the past the first and second long-term due to the limitations of industrial manufacturing technology