Hook Rollers : Rollers which prevent the lifting of the resolving upperstructure from the roller path. Hook rollers are the means to connect the upperstructure to the foundation or pedestal. (Spec 2C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}