求翻译：以划线方式检测工件轮廓的方法与检测孔类似，双划线也刻划在检具型面上，采用比较法对覆盖件轮廓精度作出评价。当轮廓精度要求较高时，可采用齐平比对方式进行检测，这时评价工件轮廓精度的依据是检具的相关型面，且应具有足够的利用长度L（25～30mm）。实际检测时，往往还需借助专用量具。是什么意思？

Workpiece contour crossed detection method similar to the detection hole pairs crossed it also depicts the type of surface in the gage, the use of comparative law to cover the contour accuracy to evaluate. Contour accuracy is higher, can be used to flush the way to detect, then the evaluation of the