Bench Marks 5 : Permanent reference points of known elevation usually placed on concrete foundations, or on top of an iron stake driven securely into the ground. (SSWID)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}