I read an article a few weeks back which was talking about the fact that the practice of knife sharpening was dying out in some developing country and thought to myself: "well, it’s still alive and kicking in a first world country (Spain)". Ever since I first came to Madrid I have seen these men sharpening knives on the streets all over Madrid. They always carry a sort of whistle with them, which they blow to catch the attention of (mainly) housewives and will then, for a small fee, sharpen the knives. In order to do this, they simply peddle away and sharpen the knife on the circular stone which stands between the handlebars.
The above picture was taken on c/ Arenal, just a few steps away from the Plaza de la Villa.