At primary school we had a lid as a desk, and I used to place rulers and a protractor in a certain combination that would be dislodged if open. OK it could pr

At primary school we had a lid as a desk, and I used to place rulers and a protractor in a certain combination that would be dislodged if open. OK it could probably be reproduced, and I don’t think I recorded what the position was, but I was only 10 at the time.