Thatr rod is a "steel" and it doesn't sharpen, it just conditions or hones the blade edge. As you use a knife, the edge is bent from striking the cutting board. The steel or hone realigns the bent edge so it's straight again.
Knives have to be periodically sharpened to keep an edge that can be honed. In other words, the steel will only work to prolong the sharpness of a sharp blade.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan