AC hole in firewall

I need to cover up my ac holes in my firewall where it hooked in. I had to pull it out to clear 20s. I want something to cover it up temporarily, not weld sheet metal to it. Got any suggestions?

if its purely temporary then you could rivet a piece of sheetmetal and seal with silicone. but of course i have to say so i dont get ripped, i suggest this with the idea you intend on welding it close at some point.

i'd do what jasonm said, but i'd just use sheet metal screws

tape some cardboard over it

eh be ghetto... duct tape that shit!

Duct tape and carbboard. PERFECT. haha. I know its ghetto, but its only until I find out if my ac can be notched or if its gone forever. ahh. thanks.