Sentence:  Opposite every gate was a hitching post or a stone carriage step , set with a rusty <WSD>iron</WSD> ring for tying a horse . 
Meaning of the word marked with <WSD> tags:  a heavy ductile magnetic metallic element; is silver-white in pure form but readily rusts; used in construction and tools and armament; plays a role in the transport of oxygen by the blood