Safe

Squinting at the numbers on the combination lock for our storage shed, I thought I would be able to feel in the late twilight the hidden grinding that signals the moments to change directions, then stop and pull. But it didn't open, and I had to turn again, squinting harder and moving slower.

I don't even know what the inside of a combination lock looks like.

It could have been a beautiful, allegorical mystery, but then I went and looked it up:
http://www.howstuffworks.com/inside-lock.htm

Or the long version, with animation and (on the second page) detailed instructions on "high road" safecracking:
http://home.howstuffworks.com/safecracking.htm

But if you're short on time, just read The Amazing Adventures of Kavalier and Clay. You won't learn how to pick locks, but sometimes pretending is better anyway.