Deadly Chainsaw Mistake.

Making a major chainsaw safety feature useless without knowing it. I see this catastrophic error again and again. A quick quiz (with answers!) to see if you know what it is.
My guess - you won't be able to spot it. So as not to spoil the fun, if you guess correctly and put it in the comments I will hide the comment (nothing personal)!
So all the guesses you read in the comments are incorrect.