They'll never do it until you show them the sneaky method!
The Secret:
Start doing the drawing like this:
( Obviously you make your line touch at the corners and in the centre. We've just put gaps here to show how to draw it. )
Once you've got this far then you're stuck... or are you?
To draw the last bit, fold the edge of the paper over !
Now you can finish the drawing and you haven't taken the pencil off the paper!
When you open out the paper again, you'll get the diagram as it should be.
This sneaky trick might seem obvious now you know what to do, but if you try it on someone they'll be worrying about it for hours!