barriers — anything built or serving to bar passage, as a railing, fence, or the like: People may pass through the barrier only when their train is announced.
guards — to keep safe from harm or danger; protect; watch over: to guard the ruler.
ramparts — Fortification. a broad elevation or mound of earth raised as a fortification around a place and usually capped with a stone or earth parapet. such an elevation together with the parapet.
securities — freedom from danger, risk, etc.; safety.