Sentence:  Maccario, it was evident, did not care to take the risk of blundering upon a picket, and a man led them by twisting paths until at last the hacienda rose blackly before them. Appleby could see it dimly, a blur of shadowy buildings with the <WSD>ridge</WSD> of roof parapet alone cutting hard and sharp against the clearing sky. 
Meaning of the word marked with <WSD> tags:  The highest point on a roof, represented by a horizontal line where two roof areas intersect, running the length of the area.