There’s a lovely PDF here that talks about open mesh floors and the ‘DARTINGTON – INSPIRED’ UNDERFLOOR ENTRANCE showing you how to make it.
The advantages are listed that
It stops wind roaring through the entrance as it’s no longer a direct way in to the hive.
You don’t need a mouse guard as they can’t get through the 8mm gap
Wasps and other robbing insects have two sets of guard bees to get through – first on the landing board and then at the verticle entrance.
And then it’s easy to close the hive completely as you just put a wooden block across.
It reminded me of a photo I’d seen the other day – which gives the bees a wide tunnel entrance going along the entrance block. This looks very interesting too and I suspect my husband will be making me one of these next year – I’d like him to make me the under floor entrance to try too.