The grommets on your shoe (Holes through which you place the lace) act as the pulley. When you tighten at the top it restricts at the bottom and compresses around your foot.
The same can be applied to a pulley; If you have the proper set up Pulling one string causes two actions; the first being the most obvious. And the second being its effect. The Grommets of your shoe are the pulley's; while your Shoelaces are just the rope with which you operate the pulley.
