Everything in a modern automobile is belt-driven. These are the timing belt, the alternator belt, and the air conditioner belt.  Moreover, if the last two burst on the road, you will most likely be able to get to a store or service station on your own. But if an unexpected break touches the timing belt, the car will not only not go anywhere on its own, but will also have to spend on the engine overhaul, if we are talking about motors with a yoke piston group.  Therefore, the tension of the belt on each node is regulated and to avoid unpleasant situations, the tension must be correct. And you can check it with this device. It will show the exact Newton meters, which are necessary for the operation of the units. The meter is made of steel and the handle is notched for convenience.