C0 no pin
Control pair, no pin on either side.
C1 no pin
Nothing crosses this join.
C2 pin_start
The leg carries down into the next section.
PIN START TO END
C3 pin_end
and is picked up here, so the line must be unbroken.
C4 no bottom pin
Nothing leaves this section.
C5 pin_end alone
A top pin with no leg above it to meet.
C6 pin_start
Into a section the line runs the whole height of.
PIN START TO THROUGH
C7 pin_through
The leg runs through this content on purpose.
C8 pin_start
A leg with nothing below it to connect to.
PIN START TO NOTHING
C9 no top pin
So the leg above dangles into this heading.