Just for the record, I did put 1/4 " hardware cloth on all sides AND the bottom of my pen with screws spaced 1/2" or less about 2,000 used! It has kept the rats out and the hens safely inside! I have not had an issue with any hurt feet or toes despite the rats continued displacing of the sand -about 80 lbs from under my 4'x6' pen. I can hear and have seen the rats trying their best to get in to no avail. 
