When they discover a slave out of the training rooms without permission, they have to investigate. They push him to the floor and detain him. As they ask him questions, they step on him. As the questions get harder, they start to step on his neck more. The love to see him struggle with the answers as they step on him. They know when he is lying so when he does, they increase the pressure, choking him.
When Sanja decides to do something, she loves to excel at it. She knows that her slave will lie still for her so she puts him on the floor. She steps onto his neck, choking him. The longer she stood on two feet, the more comfortable she got. She then started balancing her weight on one foot. She watched her slave gag and choke but he knew better than to move and stop her balancing act.