How do I make an object invisible but still functional?

"susannesims;c-17930504" wrote:
Hmm, wonder if this will come in useful with Cottage living *ahem* Llama and Cow shed *ahem*

I did it one month later in August 2021 ;)
https://forums.thesims.com/en_US/discussion/992682/i-build-a-barn-for-my-cow-then-an-invisible-animal-shed-lol
I shared my whole journey while doing it too lol. Only saw this now though :/