The more cover you have the better your chances of NOT being seen. If you do leave one side off then try to make it towards the area the deer aren' t going to be. Take wind into mind also, I' ve had deer almost walk right up to me when I was just standing next to a tree because the wind was just right. I' ve also built blinds with only one side, but I new the deer were only going to be in the area I was facing(for the most part). It really depends on your location compared to where the deer are. Hope this helped, good luck to you and your son.