A Surface plate is a solid, flat table used to gauge the accuracy of a plane surface in layout, tool setting, gaging, and inspection activities.
There are two types of surface plates. A granite surface plate or a cast-iron surface plate. Granite is considered the best material for surface plates because of its properties such as surface hardness, no rust or corrosion, low thermal expansion result in a very accurate, stable and precise surfaces. Apart from surface plate a comparator stand is required where the surface plate has to be mounted for precise measurements. Gaging accessories and layout and marking tools are required for dimensional measurement, inspecting, marking and layout, etc.