This is a reef knot:
And this is a granny knot:
Before you read any further, it might be a good idea to make a reef
knot and a granny knot. You do not need coloured string - it can
even be done with shoelaces!
Can you see any differences between them?
When a reef knot is pulled tight it looks like this:
When a granny knot is pulled tight it looks like this:
... or this:
Which do you think is the best knot for making things secure?