I have been plugging holes in my workshop lately, adding a few things and improvising others. One of the things I have been stuck with is making a DIY light-duty anvil. Nothing major here. I don't do blacksmithing. Only the occasional straightening a bent nail or piece of metal. I figured that instead of buying a real anvil, I should just find a block of wood and fix a thick sheet of metal on top. Wood block has been improvised by nailing three 2x4s on each other. But I spent a looooonnng time thinking about a heavy sheet of metal, but got nothing.

My wife threw a few pots and pans, and I investigated them, but they were not thick enough. So, the question is: can you think of anything that is available in most stores, or around us, that is thick enough for this purpose ??

I am looking for anything that is about 4x4 inches.
No problem if it was rectangular or circular, but should be around 5 mm thick ± .

Thank you