求翻译：工件正确、合理的定位是准确测量的基础。覆盖件在检具上的定位方式主要有两种：①将面定位块与工件的自由曲面贴合，再以工件上的两个孔作为定位孔，共同完成定位。两定位孔之一必须能在两个方向限位，可采用锥形塞规（用于圆孔）或棱形塞规（用于腰孔）定位；另一定位孔则只能在一个方向限位，可采用棱形销、削边销（用于腰孔）或圆销（用于圆孔）定位，参见图4。②将面定位块与工件自由曲面贴合，再在工件轮廓边缘上设置挡块，共同完成定位。轮廓定位点通常设置三点，即一个方向上设置两点，另一方向上设置一点。是什么意思？

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Workpiece correctly, and reasonable of the positioning is accurate measurement of the base. Coverage is in the position on an There are two main ways: 1 block and the free surface of the workpiece, and how to fit on the workpiece as the two holes together to complete the hole. One of the locating ho

Rational positioning of workpiece properly, is the basis for accurate measurements. Orientation of panels on the gauge there are two main ways: ① the surface position and workpiece surface lamination, with two holes on the workpiece as the positioning holes, comple