Place a dowel on the edge of the desk so it sticks out 5 cm.
Use 2 pieces of duct tape to hold the dowel in place-one close to the edge of the desk and one toward the end of the dowel.
Attach a binder clip under the zero position (middle) of the half-meter stick and flip both metal loops up.
Hang the lever arm on the dowel. Adjust the location of the clip on the half-meter stick until it balances.
Slide a wedge-shaped eraser on the end of the dowel.
The mass lifted by the lever is the load.
Hang the load, using the rubber band, on one side of the half-meter stick. The effort is the force (push or pull) needed to lift the load. You can move the load up and down with one finger.
Work with a partner to assemble a lever system like this one demonstrated in the Snapguide.