A wrench comprising (a) a catch, including teeth; (b) a fixed part defining a first jaw, the fixed part including two teethed parts permanently attached to the fixed part, the fixed part configured so that the two teethed parts intermesh with the teeth of the catch; (c) a moving part, defining a second jaw, such that the first jaw and the second jaw define the jaws of the wrench; and (d) a spring, whereby: (i) the two teethed parts attached to the fixed part which together serve as a guide for the moving part that is movable inside the fixed part, allowing the catch, the fixed part and the moving part to slide over one another; (ii) the catch is located in, and attached to, the moving part and selectively fixes the moving part to the fixed part; (iii) the spring pushes the catch in a direction perpendicular to the longitudinal axis of the wrench against the two teethed parts; and (iv) the fixed part serves as a gripping handle with a jaws of the wrench at its end.