Hi,

I use 1/2 inch plywood.  At approx $12-$15 per sheet divided by 10 =
$1.20-$1.50 per inner cover. Want top entrance cut v-notch.  Need feeder
hole drill one. They are strong and last.  Compare to $5-10 from bee supply
companies which don't hold up to real work with bees. Bee space, well, they
don't care if there is any proper space.  Get your supers on early as far as
wax on inner covers scrape it and harvest it its worth something you know.
If your not strong enough to pop cover get one of those  jumbo hive tools
that'll take care of it.

Clay