V210 hardware question

Okay: Really stupid hardware question. I'm trying to remove the PCI card from a V210 I just bought, and I can't figure out how to release the internal PCI
lockdown. The little green fixture has a round piece that seems important, but I don't want to break the thing and then find out that I can't remove the
card ever...

The hardware manual ( ) is only somewhat helpful, telling me to remove the internal PCI lockdown (duh!).
My curiosity overcame my fear of breaking it. I used a pair of pliers on the green knob-looking thing and it came up with a little pressure.