Abstract: A wrench includes two mutually movable jaws that are mounted by means of parallel linkages to a housing forming the handle. A rod is axially movable in the handle by means of an internally threaded sleeve extending into the bottom of the handle. The rod is connected at its top, by a pivotal link, to the top of the outer member of the parallel linkage. A locking member is pivotally attached to the housing and there is pivotally connected thereto, a wedge-shaped member that is adapted to engage a locking sleeve loosely mounted on the rod. The rotation of the threaded sleeve adjusts the distance between the jaws, while the engagement of the stop member with the locking sleeve prevents the movement of the jaws when they are in a working position.