Learning Command insisted that all kneepad chinagraphs were attached to suitable bits of string (usually para cord) so that if dropped, the chinagraph wouldn't become an arse looticle. Neither were students allowed to use the top pencil pockets in case something should fall out during negative 'g' manoeuvres.
The supplier of chinagraph 'leads' changed some time in the '70s and the new ones were dreadful - much softer and greasy.
Personally, after leaving training, I preferred the Staedtler Lumocolor and would buy my own.
A pen torch was also a useful item and I always had one in my top pocket. For some reason the groundcrew hated them, but they were vastly better than the official rubbish.
I still have a collection of various chinagraphs stuffed into a pot somewhere - liberated from sqn ops when the chinagraph and Perspex gave way to whiteboards and dry markers. Then came the infernal IT-based system which was infernally slow and inflexible.