Denotes a "recommended practice(s)" (1) where a safe comparable alternative practice(s) is available; (2) that may be impractical under certain circumstances; or (3) that may be unnecessary under certain circumstances. (RP 49)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}