<p>Stepped roller pins roll within stepped lobes formed around the interior wall of a hollow cylindrical casing. A hollow cylindrical retainer or simple ring retainer hook into a recessed groove around the middle of the roller and interact with ridges or grooves in the casing to retain the rollers within the lobes. The retainer fits within the limits of movement of a larger diameter section of the roller so that maximum contact is made between the rollers and a smooth stud shaft which is encircled by the casing to any desired extent. The rollers move along the lobes until they lock tight to grip the stud shaft for threading or unthreading. The casing is provided with wrench gripping faces around the exterior. A wrench grips the casing from the side to operate it leaving both ends of the casing open to admit the stud shaft.</p>
