A sub in which a free-floating ball rolls to the low side and opens a port indicating an orientation position (refer to "Hydraulic Orientating Sub"). Sometimes abbreviated as BHO sub. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}