Life is teeming with unwritten rules. Laws that no one tells you, but which everyone seems to have an opinion about. In this column, they take a closer look at a situation or occasion every week: how does it actually belong there? This week: the five rules of the game as a volunteer. Research by Lonneke Roza, who obtained her PhD from the RSM on the subject of corporate philanthropy, shows that about 10 percent of employees who work for others do not volunteer in their own time.