In order to measure flatness deviation, you will need to use it with a ruler Designed with a vernier which can help you to read the measuring result easily,it is a great tool in your engineering inspection project This feeler gauge can be used to measure for widths, and also flatness deviation 0.2/0.5MM ,you can choose the detail size feeler gauge which more suitable for your use.small size and light weight, there is a strip on handle so that carry it conveniently This vernier feeler gauge can be used for house inspection, engineering inspection,home and professional use, Manufacturer: XIAOQENAN