hehe. if you thought lead was toxic, in a textbook we have from the 1970s about hand drafting and sketching, on the very same page lesbian rules are mentioned it notes the following:

Pencil lines or dirt can be removed from tracing cloth by rubbing lightly with a cloth moistened with carbon tetrachloride (Carbona) or benzine [sic] (Energine). Use either with care in a well-ventilated area.

we also have a couple masonry textbooks, and lesbian rules in masonry applications look to be very antiquated, at least from a quick peek at them, sadly.

then again we did yuri with another girl irl on a brick construction site recently! perhaps the true lesbian rules were the girls and fembys we kissed along the way