A Golf club iron groove sharpener.
Over time the wear and tear on your irons takes its toll and the amount of spin you generate reduces.
One end is for V and the other end is for U grooves.
This handy tool will put life back into your irons and give you optimum spin back as if the clubs were new.
Therefore you will reduce your score because the ball will be nearer the hole.
Simply run the sharpener down the grooves as and when required and it will add bite and sharpness.