Abstract: Apparatus for an anti-rotation mechanism, such as used in a wrench. The space between a pair of races contains a plurality of pairs of rollers. One race has a protrusion centered inside each pair of rollers, with the rollers biased against the protrusion. Adjacent the protrusion and between the rollers of each pair is a prong that selectively biases one or the other of the rollers of the pair away from the protrusion. When one roller in the pair of rollers is biased away from the corresponding protrusion, relative motion between the pair of races is enabled in only one direction. The protrusions extend into the space between the pair of races sufficiently to prevent the rollers from moving under load when relative motion is inhibited.