Screen Barrier under shed ?

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I probably wouldn't bother. As I walk around the island, I don't see many places that have barriers to access under the camp/sheds. Our camp and two outbuildings are all on piers, open to the world except for trim lattice on the front. Bees, etc tend to build in the eaves, not under the building. The problems we've had were with tiny critters, mice, chipmunks that find ways in at higher levels, like a little crack around a door or window when the building settles. Unheated buildings tend to not be well sealed.
You can buy either plastic or pressure treated 2" lattice, staple screen to it and install to cover the 8" gap, maybe with a few inches dug into the ground if you like. This will look better than 1/4" hardware cloth and being rigid should be easier to work with.