If you have ever went to see a concert, play, musical or any other performance on a stage, it is very likely that there were curtains involved. Tonight, i was partly responsible for the curtains at the IHS Talent show. The contraption that allows the curtains to move across the stage is a simple pulley system using two pulleys and a rope in-between. When the rope is pulled in one direction, it creates a torque on the pulley and causes it to spin. This spinning either opens or closes the curtain (depending the direction pulled). This contraption is also very common with close-able curtains in your home. And this is a very simple example but i realized thats some of the most simple things help the most!