That appears to be the procedure for fault-finding problems with the power steering (when there's no exterior leaking).
Check the pressure of the system when the temperature is "normal"; if the pressure is also normal there's no fault.
If the pressure is low, but you can build it by shutting the tap in that tool; the rack is damaged (I think the term "gear" is confusing).
If the pressure doesn't ever build with the tap; the pump is damaged.
It is useful to check the pump, but I suspect it's not the kind of tool most people would have.