There are often black (or sometimes other colored) rectangles printed onto the foil that covers many chocolates. The foil is usually folded in such a way that the rectangle is on the back of the chocolate. The rectangle itself is sometimes printed off the edge of the foil so that the whole rectangle is not on the foil. And sometimes there is more than one rectangle, and they are different sizes, even on the same piece of foil.

What are these rectangles for???

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