DA recommends not using pendaflex-style hangers. Instead, he suggests just stacking the manila folders against themselves, possibly propped up by some metal plate at the back of the filing cabinet drawer.
Personally, I have never figured out what metal plate he's talking about. None of the filing cabinets I've ever seen have anything remotely able to prop up a drawer full of manila files. That said, I faithfully followed his advice for some time, using a couple of large books to prop up the manilas.
But it was messy.
So - are people using hangers or not? If so, do you stick with one manila per hanger? Isn't that expensive (in money and in space)?