פירוש על קידושין 44:15

Hazakah is an act that creates the presumption of ownership. To acquire a slave through hazakah, the slave must act in a manner subservient to the one acquiring him. The baraita therefore describes common things that a slave would do for an owner. Note that most of these are acts of personal servitude. It seems that most slaves served as personal servants and not workers in the field.

At the end of the baraita R. Shimon makes a cryptic statement regarding hazakah.
R. Ashi explains that according to the tanna kamma (the first opinion) if the slave lifts the master, the master acquires the slave, for this is an act of hazakah. The slave shows that he is a slave by lifting the master. But if the master lifts the slave, there is no acquisition.
R. Shimon disagrees. In general when one lifts something up he acquires it. Thus hazakah should not be greater than lifting means that whenever someone lifts something, he acquires it. Even if the master lifts the slave.