Amolador is the portuguese word for grinder, or knife sharpener. These skilled knife sharpeners push their bikes through the streets, playing a distinctive tune on pan flutes to signal their presence.
Their bikes serve as a mobile workshop, with a sharpening stone mounted on the top tube, a tool box strapped to the back, and umbrellas draped over the handlebars.
Apparently there used to be many amoladors, but with the advent of cheap knives and scissors it's a dying profession which is too bad because it's pretty cool.
I found a popular portuguese saying, "quando há amolador, há chuva": when the knife sharpener is around, it's going to rain.