I don't understand one bonus...????

Will someone please tell me which buildings are "Production Buildings"? I don't know when to use the bonus that makes Production Buildings produce 2X more. I know the other one that makes production faster, but not that one.

Thanks fishes.

The production buildings are the ones that keep spitting out supplies on a continual basis unlike the depositories which have a limited amount which the zombies have to go in after. Hope that helped.

Yes it did. Thank you very much for responding.