I see there are a huge variety of Mating NUC entrance disks for sale - Dave Cushman's site shows quite a few examples.
But I just don't get them. I understand the 'lots of fine holes' for 'Closed - with Ventilation', and I understand 'Fully Open' - but why the intermediate settings ? Why, in particular, is there any need for a Queen Excluder option ? Surely she's either confined (along with the rest) - free to fly (along with the rest), or quite happy laying eggs with the door wide open ...
What am I missing ?