Nobody has ever told them to me, not that I can recall. But I know the rules. As long as I keep my whole body completely under the blankets no monster can get to me. Not my head, of course, if anything bad is in my room, I want to be able to see it and at least stand a chance. I do not understand how other children keep their heads hidden beneath the covers and think that will keep them safe. It makes no sense at all. I have to be able to see the door and the window, that is where the danger lies. Not in the cupboard, I checked that out before turning out the light. Just like I looked thoroughly under the bed.
My toes and my hands are the trickiest bits. So often I wake to find that they have escaped and have to hurriedly whip them back to safety. That is all it takes, one little piece for them to get at.
There have always been monsters that come to hurt you during the night. Every child knows this. You just have to follow the rules and hope for the best.