I think they both mean the same. The indication is that it was quickly put up, perhaps not for permanent use.
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New2grammar I feel you're describing the meaning of adhoc.I don't think so. You could come upon a fence in a pasture and have no idea of it's purpose or the circumstances under which it was built, or how long it's been standing. Yet, knowing something about fences, you're able to judge that it was improvised.*****
Grammar Geek with the full intention of dismantling it afterwards.Thanks, GG. I hadn't picked up on that aspect of it. That's important.