Blind Rams 3 (Blank, Master) : Rams whose ends are not intended to seal against any drill pipe or casing. They seal against each other to effectively close the hole. (RP 53)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}