I use a piece of plywood cut 1" larger all around than the unit and
hold it in place with something heavy.....like a rock or a concrete
block.

Yeah but we dont all live in a trailer.

===========================
Well I sure as the devil do not either...
BUT that is how I protect my outside unit....

Only attempting to keep out leaves and allow air to circulate..
Both my sons are in the heating and a/c business they both
told me that 99 percent of the units they see with rust problems are
the ones whixch are covered ...

I use a pretty "rock" to hold the plywiid down ...lol

Bob G.