Way I do it is 1/4 inch hardware cloth, cut a rectangle maybe 7″-9″ by 15″ to 17″, make a half tube, wider at the top, put the wide end to the hole or gap, staple the screen down to the shingles, siding, whatever surface you’re on. Bats have to land and crawl in, they don’t just fly in a hole like a bird. If it’s vinyl, brick, LP etc… tape works, but be careful what you use. Bats can’t chew, so it doesn’t need to be anything super durable. This applies to things like soffit gaps, what we call “overlaps”, I think the technical term is soffit returns, siding holes, whatever. If it’s something like a fascia corner or drip edge, where you don’t have a long enough flat surface to attach, you can still use the screen, just make a full cone, and make sure you angle it down a a decent angle, or you can use aluminum flashing. If you look online, it’ll tell you you need a valve or, some window screen or something at the end, in my experience you don’t, as long as you’re gonna seal it up quickly, just extending the entry away from the hole is enough. Hope that wasn’t too long winded…