Just use regular screws of the right length and thread - some are English and some are metric. Don't even bother with flatheads - standard panheads are more durable, and there's really no need for that back edge to have countersunk screws. They won't be captive anymore, but so what? If you lose them, just put in fresh ones. You'll never have to struggle with this issue again, so no more screw anxiety.
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Ed
