A trick to replacing floors

This might be commonly known, but I wasn't able to find any info and it was driving me crazy, so perhaps I can save someone else the headache. In short; a Placeholder Wall seems to actually seal an empty floor space.

I started with the Ryokka TU-76a Salvage Tug, which has all the broken duplicate parts. The mish-mash of floor types it has is visual clutter I don't want on such a small ship, I'd rather it be uniform. Switching out a dozen or so floor segments is not a quick process and repressurizing/heating your ship after isn't either.

So I got the bright idea to build a wall on the section to remove, swap the floor, uninstall the wall, and repeat. Which worked. No atmo vented but moving the wall segment quickly became tedious. Curious if just the Placeholder (placed to install but not constructed) would serve and... to my surprise it does. No hissing of air escaping or my O2 alarm going off. Doing it that way saved me a hell of a lot of time.