Yes Jim, it is a dedicated little box for a middle entrance. I need an entrance above the ground to keep the skunks from destroying my hives. So the easy options are a middle entrance or a top entrance. Personally I don’t like top entrances in the summer because as soon as I remove their entrance, there is a huge swarm of confused bees flying all around me. That un-nerves me a little, so I like a fixed entrance that doesn’t have to move....like the bees expect in their natural habitat (ie trees).
The little mid entrance box is also used for drone culling for varorra using little 2.25” foundationless bars. I believe this also allows the queen to find as many drone cells as she wants without wondering into the supers. The extra space is also useful when compacting the hives down to a single box for winter.
The downside of this little box is it’s another piece of equipment. I’m not totally sold on using it forever, but so far it has served it’s purpose.