What he means as backbone is how u identified it as the main clause or main verb ?
am i right believe?
Yes, I was not sure how we could say SUMMARIZE is the main verb and DOES is the helping verb.
But, I guess the following is the answer:
"Helping verbs or auxiliary verbs such as will, shall, may, might, can, could, must, ought to, should, would, used to, need are used in conjunction with main verbs to express shades of time and mood.....in simple present tense, do (does) will function as an auxiliary "
....really, before this discussion I thought the ans. to my Q would be some "idiomatic" type thing "No rules. Just right" until Himalaya indicated that there is some logic involved.