Sentence:  Nanny Broome was looking up at the outer wall. Just under the ceiling there were three lunette windows, heavily barred and blacked out in the normal way by centuries of grime. Their <WSD>bases</WSD> were on a level with the pavement outside, a narrow way which was several feet lower than the road behind the house. 
Meaning of the word marked with <WSD> tags:  A supporting, lower or bottom component of a structure or object.