Sentence:  There were umbrella tents , wall tents , cottage tents , station wagon tents , pup tents , Pop tents , Baker tents , tents with exterior frames , camper trailers , travel trailers , and even a few surplus parachutes <WSD>serving</WSD> as sunshades over entire family camps . 
Meaning of the word marked with <WSD> tags:  serve a purpose, role, or function