Naomi told Ruth to make a note of where Boaz slept and to quietly uncover and lay at his feet. In the culture of the day, this act was understood as one of total submission.
At midnight, Boaz awoke, startled to discover a woman lying at his feet. Ruth presented her request humbly enough by saying she was his servant, but was appropriately bold enough to take her in marriage: “I am your servant Ruth,” she said. “Spread the corner of your garment over me, since you are a guardian-redeemer of our family.” This statement was a culturally relevant way to say, "I am a widow; take me as your wife."
Attracted to her virtuous character, Boaz readily agreed, but there was still one more obstacle to get past.