"See, how they work," the first said, "is the right lens is polarized vertically and--"

"Wait, what do you mean by 'polarized'?" said the second.

"A vertically polarized lets no horizontally polarized light in, and a horizontally polarized lens lets no vertically polarized light in," said the third. "If two perpendicularly polarized lenses are put together, no light is let through."

"So as I was saying, the right lens is polarized vertically, and the left horizontally, or vice versa, such that each eye sees a different picture."

The second had an idea. "So that means if I..." He closed his right eye, and smiled. "Yes, I can only see your right eye."

The fourth and final person (you, of course), sensed something wrong. First, you verified the second's observation. Then, you said...

Aren't left and right always relative to the individual? If we stand opposite to each other (facing each other) then my right side lines up with your left.

That being the case, if the glasses are all the same, i.e. vertical polarization on one particular side (either lL or R), then the same type of polarized light (either V or H) will travel through all the R lenses, and the "other type" will travel thought all L lenses.

However, there is one more factor...