According to Google, witness marks are “an intentional, accidental or naturally-occurring spot – a line, a groove, or another contrasting area – that serves as an indicator of how things previously were implemented, used, repaired, or what processes were followed,” but in this episode we find out that the Crain siblings (specifically Steven) did not know how to read them… Typical Steven bevahior, smh. If only he could read those witness marks that were always there, a lot of hurt could have been avoided. It wasn’t mental illness, Steven! It was the literal ghosts that haunted you that one summer you and your family lived in Hill House!
Article I referenced when I mentioned that Steven might be a psychopath:
The Haunting of Hill House Recap: He Ain’t Crazy, He’s My Brother
https://www.vulture.com/2018/10/the-haunting-of-hill-house-recap-season-1-episode-8.html