I just used the little bit of cutoff wood from when I trim the 1" x 6' x 8" boards down to 1" x 6' x 6 & 5/8ths" then some 1/8ths inch hardware cloth which I now have a lot of thanks to buying a full roll (110' x 5') just to get some for SBB's.
I'm really just amazed at how well this worked to cool them off. I got into them today and nary a one came after me at all even with the top off and me pulling out a frame of brood. Amazing, simply amazing. Thanks again tecumseh. I will never again go without robber screens on the hives that are next to my front door.