The untouched margin

Original non-fiction-style practice text.

At the lettering workshop, every learner received a sheet with an unusually wide blank margin. A visitor suggested narrowing it so that more practice lines would fit on the page. The teacher, Anwen, handed him a completed sheet and asked him to look at the left edge.

There she had tried several strokes before beginning the final lettering. On another sheet, a learner had tested how much ink the brush would release. These small trials helped them adjust their movement without interrupting a word halfway through. Some learners left the margin blank at first and began using it only after seeing how a brush behaved.

Anwen did not insist that every spare space be filled. Its value lay in being available when needed. Reducing the margin would produce more finished-looking rows, but might leave less room for the adjustments which made those rows possible. She described the blank area as working space, even on a page where it remained untouched.

Explain why Anwen describes even an untouched margin as “working space”.