I have used slotted racks with slats crosswise to the frames. Now I see parallel slots advertised. After adding beltsville screens below the racks [reversed so I can test for dead mites from the rear of the hive], I have begun to wonder whether the slotted rack will not reduce the effectiveness of the screen. I also wonder whether the hive will not be harder to defend with slotted racks in place [Last fall and this spring I have a very gentle Carniolan colony under repeated attacks from a neighbor's Italians The raiding is constant on warm days with a hive full of capped honey in the third Illinois from last year, and some of the carnies are now getting hostile toward anything that moves within 20 feet of the hive. Two other carniolan hives slaughtered Italians last year and seem not to be troubled this year. However, their queens obviously bred to some Italians in addition to the carniolan drones a year ago]. John F. Mesinger [log in to unmask]