Mistress Julia wanted her slave to remember that he had responsibilities that he had to adhere to and that she would not remind him of them again. So she chose to crush and trample his hands with her boots so that he would not forget what she had asked him to do and that he would not need to be reminded as it was his duty to always remember what he was supposed to do.
Mistress Jessica is a hot girl and she knows it. A lot of guys want her and that made her proud and got her doing things unimaginable things. Today the mistress used her feet to trample on this guy who was interested in her. He had done nothing wrong to her, but she was doing it because she could and because she could get away with it. She used her boots to do it.