An adjustment tool (10) for an external fixator for exerting a compression or distraction on a broken bone fixed by bone pins (2) spanned over such a fracture comprises: a fitting element (12) for holding fast a clamping assembly (3) of the external fixator, a positioning clamp (11) for fixing the adjustment tool on a rod (1) of the external fixator near said clamping assembly (3), and a connecting element (13) attached to the fitting element (12) and the positioning clamp (11) adapted to move the fitting element (12) towards to or away from the positioning clamp (11). The fitting element (12) comprises a blocking sleeve (122) adapted to push the uppermost jaw of the clamping assembly (3) in the direction of the longitudinal axis of the clamping assembly (3) to block the second upper most jaw against an abutment portion (129) of the fitting element (12) and further comprises an actuation element (123) within the blocking sleeve (122) to actuate the locking element of the clamping assembly (3) for releasing the rod (1) of the external fixator within the clamping assembly (3) without releasing the bone pin (3).
