Letter: Letters: Keeping in style

From F. G. GRISLEY

Apart from mirror handwriting (Letters, 22 May and 12 June), there is
another curiosity.

Writing at a table, the arm rests, and most movement of the hand uses the
wrist.

Writing on a blackboard, the whole arm is used, which brings the elbows and
shoulder into play.

Why is it that such different movements produce identical handwriting?

F. G. Grisley
Barry, Glamorgan