The webmaster of a small home plating website claims to use multiple variable voltage/amperage power supplies, he says he wires them up in a "master and slave configuration", because we need current more than voltage I'm assuming he's somehow wiring multiple supplies in parallel. Opinions on this?

So the power supply has 120 volts going in and two terminals supplying 12 - whatever volt DC. I obviously know how to wire batteries in parallel but how could power supplies be wired in parallel? I mean I cant take the 12 VDC + from the first PS and wire that to the 120v input, what am I missing?

He claims to be using 3 70A power supplies to provide him with 210A.