guards

That portion of the main deck that extended beyond the width of the hull. On larger boats the overhanging guards on either side increased the main deck area by several thousand square feet; this allowed a much greater cargo carrying capacity. The term "loaded to the guards" means freight has been heaped aboard until the main deck guards are flush with the surface of the river. The word guard is used inasmuch as it serves as a protection against collision for the hull and also helped deflect floating objects.