Parallel to the flat foot is the standard by JB/T7977-99 manufacturing, parallel to the flat-foot material HT250, by scraping or precision face grinding. 
 Parallel to the flat foot is mainly used for machine tool inspection test roughness and non-straightness, the two face is in line with the block rules, micrometers, levels and other equipment testing different heights, the two parallel rails and not the level of rail connections, and can with the rectangular device, testing can not only test the two-foot rectangular parts of the verticality of the gauge, parallel to the flat foot also applies to equipment installation and inspection.