Chinagraphs!
When I first started my Nav exercises in South Africa, my instructor repeated over & over CHINAGRAPHs.
They are awesome pencils use anywhere jot notes on the plastic clip board, window, mark the horizon & of course on the CRP 5
Though recently got a new pooleys CRP5 it does say not to use chinagraphs, Why I dont know..... I find it easy to rub off & no marks.
Anyone else know/experience why?
My thoughts great pencils bit pricey in an art shop, so buy a couple of boxes off ebay. I find the red ones work best.
I know now why my instructor went on & on about them. Just my little input hope it helps.
Goodluck with your exams