Taking a bearing

I edit the newsletter for my orienteering club. On Saturday I lost count of the number of newcomers I gave a lesson to on how to use a compass, so have decided to write a pictorial guide to using a compass which will go in the next edition. 
Spent ages taking photos and writing the instructions  on how to take a bearing from point 3 to 4 on my map. It got very late. Then I realised that  if  they followed my pictures they would make a 180 ° error. Oops. I will take more pictures in the morning. What a waste of an evening.