Mistress Dana wanted to control this guy and she eventually did it. She managed to convince him to wear a chastity device and she locked it. Once he had worn it, she knew her work was done as she now controlled him. He realized this when he tried to get it off. It did not work and he had to do what she wanted and that is how she controlled him.
Mistress Valentina wanted her man to beg for the chastity key that she had in her hands. She had made him wear a chastity device and he loved how naughty she was. But she did not go all the way and he was left with the device which he could not remove. He could not use his dick for anything other than peeing. She had fun making him beg for it.