Repairing Wooden Shack? Or Metal Door?

I see Wiki mentioning decay. I’ve also seen decay happen. How to repair?
Does all things need repair against decay? Doors? Walls? Platforms?

Thanks for any insight on this

For wood stuff put wood in your hotbar slot and look at the structure (example: wooden door) and press whatever key the wood is in. Same goes with metal objects.

Also opening and closing doors prevents decay, along with campfires.