The house where I was growing up had wooden beamed ceilings so these wouldn’t really work. They’re ideal for houses with white ceilings where they’ll blend in perfectly during the day, and also because houses with drywall ceilings have smooth continuous surfaces to apply them to.

We applied these to painted wooden planks. You just need enough surface area for them to stick to and you’re golden

The beams in that house weren’t painted, they were just bare wood (maybe stained). They might have stuck to them still but it probably would’ve looked ugly and been very noticeable since it was also darkened with age.