Actually my dad cut it (I don't do metal!)... he just used a jigsaw with a metal blade... if you do it this way, use safety glasses... the metal bits really fly!
BTW, I noticed the mice hoppers in my aquarium were crawling through the wire of the food hopper I made for the tank (it's just 1/2" hardware cloth) so I figured I'd give the expanded metal a little 'test'... I took one of the food hoppers from my rack, and inverted it over some of the mice, trapping them inside. And, they weren't able to get through the holes in the expanded metal. So, I'd have to say that 1/2" expanded flattened metal is approved for raising mice, in my opinion.
Dawn