NavList:

I don’t ever remember seeing anyone using anything other than a good hard rub with their index finger for pencil, or spit and index finger for china-graph.  Perhaps once a year you might give your Mk4B a treat and give its face a once over with a little cigarette ash.  However, I suspect ashtrays disappeared from flight planning rooms some time ago, and many of the colleagues we relied upon for a ready supply of ash are unfortunately no longer with us.  DaveP