The most prominent symbol on a Venetian gondola is the Ferro da Prua (the "iron of the prow"), the distinctive metal ornament at the very front of the boat. Every detail of the Ferro is symbolic of Venice: the S-shape represents the curves of the Grand Canal; the main "comb" consists of six prongs (or denti) representing the six districts (sestieri) of Venice; a single prong facing backward represents the island of Giudecca. The stylized curve at the very top represents the Doge’s hat (the Corno Ducale), while the small arch above the top prong symbolizes the Rialto Bridge. Beyond its symbolism, the Ferro serves a vital practical purpose: it acts as a counterweight to the gondolier standing at the back of the boat, keeping the narrow vessel balanced in the water. It also serves as a "bumper" to protect the expensive wooden hull from nicks and scratches in the tight, crowded canals of the city.