1. n. [Drilling]

Toolface angle used for deviated wells. High-side toolface is the angle of the borehole survey instrument within the wellbore measured clockwise relative to up and in the plane perpendicular to the wellbore axis; the high side (maximum build), maximum right, low side (maximum drop) and maximum left directions have high-side toolface angles of 0°, 90°, 180° and 270°, respectively.

Synonyms: gravity toolface

See: magnetic toolface,  toolface