A scotch rule is a pair of lines, one thick and one thin, set close together and read as one. It is an old device from the printer’s case, and it suits a page with a strict grid, because it adds a little ceremony without adding any new shape.
How the kit draws it
The kit has three lines. The scotch rule opens a section. An ink hairline heads a list or a card. A thin, pale rule separates rows, with none after the last one.
Why not more
A rule is structure, not decoration. If every block had its own frame, none would stand out, so the fleuron break and the plate frame are each kept to once a page.