The knockout rod on my wife's Delta 46-460 has a knob and it needs it because the rod is thin... so there's not much mass behind an unassisted knockout.
My Nova bar is much heavier, so just the inertia of sliding the bar has been able to knock out virtually anything without having to add any hand pressure on the end.
I keep my Nova bar attached to the edge of my workbench by some strong magnets at the tailstock end of my lathe. I find that I'm switching live center for jacobs chucks etc in the tailstock much more often than anything in the headstock, so it lives near the tailstock.
Maybe I'll just get another rod for the headstock end... can't have too many toys!