I bought a "hole saw" dirll bit the size of a mason jar lid. When I make my own inner covers, I put a hole that size on the cover and put #8 hardware cloth on the bottom of the hole. I can feed with a mason jar with holes in the lid AND I can refill without facing a bee. It also provides ventilation in the winter. I like the 1/4" laun for inner covers. It doesn't warp like the masonite does and it's nice and lightweight.