He or she was wedged into a triangle formed by cinder blocks which support the pond waterfall. There was no way out except forward, and she wasn't budging. And she wasn't happy.
I always thought possums were all bluff, but the closer we got to her, the more aggressive she acted. Hubby had to put the board back over her in order to unscrew the next board. I was afraid she would lunge at Hubby's hand and drill when it was next to the stone.
She also didn't like the flash on my camera, but she did close her mouth a little when I backed off. I think it is a female because of the nest of leaves she made. Perfect spot too, blocked from the winter wind and next to the side of the pond so cooler in summer too. I'd chase her off, but it probably wouldn't do any good, and possums are great for reducing the mouse and rat population. So I hope she stays and raises her broods here.