Abstract: A device anchors a tubing string within a stationary well casing against rotation in a predetermined angular direction. A housing is installed in-line in the tubing string. Anchoring mechanisms are spaced circumferentially about the housing. Each anchoring mechanism includes a recess and an anchoring member free-floating within the recess. The anchoring member has a fulcrum portion and a bite portion external to the recess. Retaining rings partially overlaying the recess prevent the anchoring member from escaping. A spring urges the anchoring member against the retaining rings and urges the bite portion to contact the well casing such that rotation of the tubing string displaces the anchoring member. Rotation of the tubing string in the predetermined direction seats the fulcrum portion in a seating structure within the recess and causes the bite portion to bite into the well casing, locking against further rotation.