Field guide / Rule 08 — Non-breaking spaces
Some pairs of words belong together so tightly that a line break between them jars the reader — 10 kg, p. 5, No. 12. The section mark was the first case; the same invisible character solves the rest.
Read 10 kg and your eye takes it as a single quantity. But the space in the middle is, to a layout engine, just another place a line may end — so on a full line 10 can sit at the right edge while kg drops to the next, and for a beat the number points at nothing. The same goes for an abbreviation and the number it introduces: p. 5, No. 12, Fig. 3, and in Brazilian legal writing art. 5.
The remedy is the non-breaking space: identical on the page, but a line is forbidden from breaking across it. Bind the space in 10 kg that way and the pair moves as one — either both stay on the line, or both wrap together. It is exactly what holds § to its number, applied to the quantities and references that fill a working document.
Because the fix is invisible, it is conservative by nature: it only ever turns a space that is already there into an unbreakable one. It never adds a space, never removes one, and only binds a pair it can recognise — a number before a known unit, or a known abbreviation before a number.
We bind two things, both from a closed list so nothing is bound by accident: a number and its unit, and a whitelisted abbreviation and its number. We deliberately do not bind name initials — J. R. R. Tolkien — because a lone letter and a dot is also how a legal outline numbers itself (A. First point, I. Introduction), and binding those would be a fix in the wrong place.
Number and unit are now unbreakable — they wrap as one.
An abbreviation holds to the number it introduces.
Brazilian legal abbreviations bind too, in pt-BR.
Initials collide with outline markers — left untouched.
mothers is not a unit, so there is nothing to bind.
In short
A value and its unit, an abbreviation and its number, are one reference each — so a line break must never split them. We turn the space you already typed into an invisible, unbreakable one wherever we can recognise the pair, and we step around name initials, where that same shape means something else entirely.
Want to see it on your own text? Convert a document and read the cleanup report — every space we bound is counted there.