In any case, the things they added could very well have been called "column-divider" and "row-divider" with much less ambiguity because not everyone who has to wrangle with CSS is a designer by profession or by choice.
I presume you’re talking about a feature like this: https://tagboard.com/product/guides-and-remote-refresh-capab...
In page layout software, the thin UI elements bordering the left side and top side of the page, with the little tick marks, is called a ruler. The tick marks on the ruler are called rules (just like the rules on a physical ruler used for measuring things). When you click/drag on the ruler elements, you create guides (or guidelines).
I’ve never seen “ruler guides” verbatim, but I would take that to be shorthand for “guides one could create using the ruler” (which would be a mouthful) to disambiguate the word “guide” when there isn’t sufficient context for the reader to likely understand what was meant.
The guides themselves are not rulers.
> A ruler, sometimes called a rule, scale or a line gauge or metre/meter stick, is an instrument used to make length measurements, whereby a length is read from a series of markings called "rules" along an edge of the device.
- there is a decision on how to measure things ( this affects prices taxes and commerce )
- there is an association between the power to enforce a standard and the instruments of that standard
- the measure instruments are generally very straight
