Abstract: A wrench, formed as an open box wrench or to completely encircle a nut comprises a drive insert for at least two opposed nut faces. Each drive insert engages its respective nut face over the full length of the latter. A guideway for each drive insert has parallel sides arranged at an angle such that upon applying torque, the drive insert will not move into the recess, while on the reverse stroke the insert will easily move into the recess. The facing surfaces of the drive insert and the nut may be provided with a cooperating projection and recess.