The plot

Trace, radius, barge. Then a head. Never the other way.

Wren does not open the rack until Joss has a pencil line that repeats.

Trace

We mark the start, the farthest the head travels, and the return. Three marks make a basin. One pretty roll does not.

Radius

Short radius is a gated player. Long radius is a flowing player. Mixed radius is a teacher problem, and the gin will say so rather than sell two personalities as one mallet.

Barge

Face-balanced heads like short basins. Hanging toes like long basins. A mismatch is a tow that will not make the turn, no matter how expensive the brass.