moon direction

On the topic of astronomy, something I realized relatively recently is this: the bright part of the moon points toward the sun. I mean, I knew the light was coming from the sun, but I didn't realize the practical implication of this: you can look at the moon, and know from that where the sun is located. If the sun has set, but it's now too dark to see where it set at, the moon is pointing there. This in turn can be used to determine which direction is West.