Around many of the old palazzos of Florence, you’ll see these sconces, made of wrought iron, with an iron hoop and sometimes with a sconce for a torch above, as in those of the Palazzo Strozzi, shown above. These are ferri da facciata or facade irons. Their purpose caused me some consternation when researching Machiavelli, as some of my (later) sources indicated they were used for hanging banners or ribbons. This didn’t make a lot of sense to me, as they seemed designed for far more durable use than that.
Indeed they were used for tying horses, as you can see in the Nerli Altarpiece by Filippino Lippi. In a detail in the background, you can see a ferro da cavallo in use:
