Normally a Polaroid is cut so that its polarization orientation is either parallel or perpendicular to the cut edges of the polarizer.   However, in the case of these polarizers the polarization orientation is at 45 degrees to the cut edges. Therefore, if you hold up two normal Polaroid sheets and orient them so you can look through them at the audience, you can rotate either of them about the "Z" axis and still see the audience. Do the same operation with the Polaroid's cut at 45 degrees will and you will go from being able to see the audience to complete blockage of any light through the Polaroid's whenever either Polaroid is rotated about the "Z" axis.