A rope is held at the two ends so that vertical and horizontal polarized waves can be sent from one end to the other. The rope is then inserted between the two cookie coolers. When the two cookie coolers are aligned, they can pass a rope wave polarized in that direction but when they are crossed no wave can pass.
This can be used as an analogy to light waves, which are also transverse waves. Technically the mechanism of polarization in electromagnetic waves is somewhat different and more complex than this model. In an advanced class, this can be used in conjunction with Demonstration M7-01: MICROWAVES - POLARIZATION.