Side point: can I suggest we all throw away whiteboard markers that don't work any more? In my experience, people will just place them back in the tray and keep trying other markers until they find one that works. There is probably someone whose job it is to replace markers, but they would just replace missing ones rather than try every single one to see if they still work. So throwing away dead markers speeds up the process.
Or use refillable markers, of course.