A screen top is just four 3/4 x 3/4 pieces of wood the size of the box, nailed together and then covered with window screen. So it's kinda like a top cover but not solid--screened. It increases ventilation down here, like last week when it was 96 degrees with 75% humidity. I actually lost a trapout hive last week because it DID NOT have a screend top and they overheated. I had them closed up after a move. I keep my telescoping tops ajar in summer due to the heat, but I don't want robbers and pests getting in.