witness mark n. generally, an intentional, accidental, or naturally occurring spot, line, groove, or other contrasting area that serves as an indicator of certain facts; in geography and surveying, a blaze, cut, hole, paint splash, or message written on a post, tree, rock or other guide to indicate a boundary, feature, or significant point on land, especially on a witness post; in construction and manufacturing, a line, groove, score, notch, cut, or written indicator made on the surface of material to impart information, such as where to cut or join; in forensic investigation, a surface groove, smear, stain, abrasion or other feature that can serve as evidence. (source: Double-Tongued Dictionary)
Further reading
Deb in Sheboygan, Wisconsin, says that when her mother was disappointed or annoyed she’d say Wouldn’t that just cork you? The idea here is that in the same way that a cork that stops up a bottle, an unexpected or irritating event...
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...
In process engineering, a witness mark can be the result of a particular process, the presence of which will prove that the process has occurred. E.g. A mark left on a test point from a test probe. However, in some circumstances, such marks are considered to be damaging and so efforts are made to avoid, prevent or eradicate such marks.