Why did Ruth uncover Boaz's feet?
In the story of Ruth, Ruth worked in the fields as a charity case to supply food for her mother-in-law and herself. Ruth didn't realize it, but the field she selected was owned by a relative of her deceased father-in-law. Boaz spoke to her, realized she was related, and made sure that she was protected (Ruth 2:8-13). He even asked her to join him for lunch (Ruth 2:14). Nothing more might have happened, but Naomi, Ruth's mother-in-law, told Ruth that at the celebration at the end of harvest to dress up. "Therefore wash yourself and anoint yourself, put on your best garment and go down to the threshing floor; but do not make yourself known to the man until he has finished eating and drinking. Then it shall be, when he lies down, that you shall notice the place where he lies; and you shall go in, uncover his feet, and lie down; and he will tell you what you should do" (Ruth 3:3-4).
Many scholars conjecture as to what this symbolic action represented, but the most sensible is that Ruth was indicating that she was willing to serve Boaz (willing to be under his feet). Boaz wouldn't hear of Ruth becoming a servant in his house. He was impressed that she had not chased after men as other women did (Ruth 3:10) and he realized that she had an excellent character (Ruth 3:11). Thus, Boaz realized that he wanted Ruth as a wife, not as a servant. Yet, Ruth had to give him a small push to make him realize that she was available and worthy to be his wife by offering to be his servant.