I remembered this allusion, from my copy, and I second Don's earlier reccomendation -

http://books.google.com/books?id=2W1Lq_nvlCQC&pg=PA15&dq=charcoal+for+snapping+lines&lr=&sig=QBtxpAnMiI82wzE_FPRdUGINdxk#PPA15,M1

I also find Red lines with some frequency, and Blue but twice.

I do also find the Red grease pencil markings in the universally fine cursive, you touched on in another thread Tim.

Not a big fan of the chalk disks, though I do pick them up on occasion, to abrade / break in a new braided line.