photo by Tamás Fehér
Some gondoliers in Venice rarely need to worry about bridge clearance, while others operate regularly in canals where it's a daily concern.
Tamás snapped this shot while visiting Venice for the most recent Regata Storica.
I've seen a few different versions of this piece of hardware.
I posted some photos of one some time ago entitled "The Fold-Down Lama", which features another one with clasps to hold it in place.