A fixed pulley, which has an axle mounted in bearings attached to a supporting structure, is one of these useful machines. Let's see how you can use it in the Chain Reaction!
Put a rope over a fixed pulley and attach a heavy object at one of the rope’s ends. You can easily lift up the object with the pulley, if you pull down the other end of the rope.
Build an Archimedes pulley system, which contains many pulleys. In this structure, each pulley halves the load, so you can easily lift up a heavy object. For example the crane used on construction sites works like this.
Tip: Since you can’t move the objects with your hand in the Chain Reaction, it can be a good solution if you put a counterweight on the other end of the rope, and you use the gravitational force to make the object move.