And it shall be, when he lieth down, that thou shalt mark the place where he shall lie, and thou shalt go in, and uncover his feet, and lay thee down; and he will tell thee what thou shalt do.
Ruth uncovered the feet of Boaz and lay under his feet. To place yourself under someone's feet was to make him lord and put yourself in subjection to him. Ruth was asking Boaz to redeem her by marriage and was promising that she would be in subjection to him as his wife.
God raised His son Jesus Christ and seated him at His own right hand. He placed all principalities, powers, might and dominion in subjection under Christ's feet and made him head over all things to the church. As believers we are all members of the body of Christ, raised and seated with him with all things under our feet.