Use 1/4" hardware cloth for mice and 1/2" for rats. I used to wonder how could a mouse push it's snout through a 1/4" hole and open it to chew on food. Well, they actually open their mouths within two 1/4" squares with the dividing wire in their mouth when they bite on the food. The small piece of food they bite off sort of falls into their mouth and they get down to nibble it up. I hoped I explained that okay. 
Brian
>>what size wire do you use on the wooden frames is it 1/4 inch or 1/2 inch squares. i'm talking about the wooden racks that are posted in here it looks like 1/4 inch in the pictures in here and can the mice and rats get to the food with just a 1/4 inch square well thanks everyone