This is just a magic trick, but he is really funny if you have kids or very young colleagues ! You do your laces in first, and you found a pair of laces who looks like the first. You attach them with a little string, and you left them fall on your shoes like they are not attached. You have the string on you finger you lift and shake your leg and pull the string in the same time, the people who looking at you think the laces are attached themselves alone ! Watch the video you will understand better.