This wedding invitation design by Cristina Moralejo takes the term "Tying the Knot" to a whole new level. When both ends of the wedding invitation are fully spread and open, the action forms a knot. Take a look at the pics below to get the idea behind the invitation. Brilliant!
Translation: LOOP THAT IS FASTENED AND LOCKED SO IT IS DIFFICULT TO RELEASE, AND THE MORE ITS ENDS ARE PULLED APART THE MORE IT TIES TOGETHER.