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:



or this:



Which do you think is the best knot for making things secure?

Why?