If I ever decide I need lids on my buckets of ff, I'm going to try these ...
http://www.usplastic.com/catalog/item.aspx?itemid=24071&catid=685
They are strainers ... I wouldn't use them as strainers, I'd use them as lids. Keep pests out, let air circulate.
That's a nifty idea. Have to keep out of the coop because they'd be standing on it.
