Loosen 1 bolt & lift rooftop tent off car

Need an extra pair of hands for a quick 10–15 minute job in the car park. A fold-out rooftop tent needs to be lifted off the car's crossbars. 3 of the 4 mounts are completely removed. On the final mount, the plastic knob is off, but there is still one metal lock-nut holding the metal bracket plate in place. Please bring a basic socket set / spanners (likely 10mm or 13mm) and a pair of locking Vice Grips to get this final nut off. The lift: A quick two-person lift to carefully raise the tent straight up off the roof bars and place it flat on the ground. I will be there to help lift. Extremely quick job once that last nut is off. I will put the tent inside the car. Photos attached. Location is takapuna shopping mall.