Hi.
I know it’s a simple task, but for some reason wire cut does not seem to work on some areas. I’m trying to cut a shaped cut, but nothing works 
Trying to do a 45deg cut on the corners. file -
Your whole object is one solid. So trying to cut it won’t work in only one corner, since the object is still connected with each other.
It’s like trying to split a circle at 1 point. It won’t work because the rest of the line is still connected with each other. And in Rhino a curve that has the same start and end point is defined as closed.
If you mirror your curve and connect them together wirecut will work
Oh, what an idiot! 
Thanks!
G