What is that?

It looks like either a section of armor, or a roof shingle.

I'd imagine the latter, cause why the hell would you try to hammer a nail through a piece of armor?

She’s also wearing carpentry equipment, so roof shingle it is.

kittey said:
She’s also wearing carpentry equipment, so roof shingle it is.

Y'know, I clicked this image solely because I thought something was odd with the costume.

In that, I thought the legs were missing, and the roofing tile was her feet.