I've been doing 'door replacement therapy' recently and haven't needed anything like that. I actually straddle the door while I'm planing the edges. That works well for me, and I just lean it against something when I'm doing the hinges and knobs. Never a drama. I have seen blokes make little stands that the door slides into but I haven't bothered.
That's a really crumby web site they've put together too, doesn't showcase the product at all well.