In the Hebrew language and culture, context is everything. Boaz was a near kinsman. He did as much for Naomi and Ruth as he could at the time, but he was a busy man. The story would make little sense if Ruth was not still desirable as men in those times viewed such things. Naomi knew she had no standing, entirely dependent on everyone, but Ruth still had something to offer. Few men could match the stature of Boaz, and his justice called for the favor of God and man. We know from tradition he was a bachelor, and roughly 70-80 years old. Ruth also had her husband’s inheritance, and she was now part of that package. The whole village knew it, and before long, someone would try to claim that prize.
So Naomi decided to push the limits of social custom, advising Ruth to make herself attractive as could be, and go down to the village threshing floor that evening. During that day, the grain would have been threshed under wooden sledges, and tossed into the air so the breeze could separate the chaff, leaving the grain kernel on the stone surface. This would be heaped up according to who owned it. As much ceremony as real security, the owner would spend the night sleeping next to his grain pile after distributing some out and making sure he was the last man served the shared celebratory meal. Under normal circumstances, the only reason Ruth might show up was to beg a share of the grain. By waiting until that moment was past, she signaled a different intent.
Waiting until it was dark and Boaz was bedded next to his grain, rolled up in his cloak, she lay down next to him and pulled a corner of the cloak’s hem over herself. The cool air hitting his legs would naturally awaken him. In those times, while a wedding might be elaborate, the central act was symbolically placing that corner over some portion of the woman’s body, informing all witnesses this was his wife — she was under his covering. Boaz wouldn’t dare take advantage of Ruth’s situation, but it was certainly acceptable, if perhaps a little embarrassing, for her to ask him in this fashion. So she did it privately, giving him a chance to decline. He had not expected something so clearly delightful, because she could have easily had her pick of younger fellows. In the context, she was offering him a chance to redeem the family inheritance and raise up a son for her deceased husband, whose name was the sole heir of Elimelech. Boaz had the resources to do this, and any subsequent children would be his heirs. A lot of social and legal issues would be neatly settled in this way.
Boaz warned Ruth there was one barrier, but he hinted it was unlikely to be a problem: There was one man closer in kinship than he. So he vowed to God he would take care of this matter quickly, then asked her stay beside him that night. If anyone spotted her departure so soon after coming down to the floor, that would be even more suspicious than her being there in the first place. So she stayed, and before dawn he awakened, loaded her down with as much grain as she could possibly carry, then sent her home.
Naomi heard with delight Ruth’s account of events. She confirmed the likelihood Boaz would act quickly, and there was nothing to do but wait.