Grids Home Depot Grids.

Those are very bad for pigs. I bought those once, and my pigs slipped right through 'em! Thanks for letting us know ~

Any pictures? Brand?

Edit to add:
I searched on their website and found these. These are the safe to use.

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This one is not safe:
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Here they are, im using them in my cage, but only for structural reasons. My walls are 11" high so the piggy cant get to them. The brand is Style Selections.

Thanks for sharing. I haven't seen that brand before. Any grids that are not 9 by 9 squares across are not safe.