Abstract: A tool to facilitate the tightening of a belt which operates between a power output shaft of an engine and a power generating device, such as a generator or alternator, which is mounted spaced from the engine. The power generating device is to be pivotally mounted with respect to the engine block. Each end of the tool of the first embodiment is specially configured into an L-shaped section. The long leg of the L-shaped section terminates in a hook with there being an elongated cut-out section adjacent the hook. The hook is to be inserted within a ventilating opening assembly provided within the power generating device and the tool then positioned so that torque can be applied to the power generating device tending to pivot such about its mounting bracket until the belt assumes a sufficiently taut configuration. The mounting bracket assembly is then fixed by appropriate fastening means to prevent pivotal movement of the power generating device with respect to the engine.