1. n. [Well Workover and Intervention]

The profiled blocks attached to the drive chains of a coiled tubing injector head. The gripper blocks are arranged in opposing pairs to secure the coiled tubing string in the injector-head chains. As the hydraulic drive system rotates the chains, the gripper blocks feed the tubing string into, or out of the well.

See related terms: coiled tubing,  coiled tubing string,  injector head