The slatted rack is designed to fit a 10 frame Langstroth hive and is generally a couple of inches deep. It is positioned such that the slats run parallel with the frames in the boxes above, for reasons we cover below.
Hive ventilation - this equipment places a layer of air below the brood box, which can be beneficial in both summer and winter.
Temperature regulation - in the Summer, the slatted rack can help the bees as they seek to regulate the temperature within the hive. Bees will gather in the space provided by the slatted rack, fanning their wings. As well as providing them with a greater space in which to fan air through the hive, these bees will be outside the main hive, which reduces congestion.
Air Flow Insulation - in Winter, the space within the slatted rack provides an insulating layer, providing some protection from cold air flowing into the hive.