riddle me this: what has keys but can't open locks?

When I first learned Thistlethwaite's algorithm, I was amazed by how it divides the possible Rubik's Cube positions into manageable groups to solve the puzzle.

The artist tried to capture the thisness of the old oak tree in her painting.

If we leave now, this'll save us time later.

You can choose this, that, or the other depending on what fits your needs.

I know this've caused some confusion, but we can fix it.

If you fixed the leaky roof, this'd save us a lot of money over time.

When asked which prize he wanted, he hesitated and answered this, that, or the other, as if none of them appealed.

At the meeting we weighed this, that, and the other before making a decision.

When packing for the garage sale, I tossed in this lamp, that lamp, and the other lamp that had been sitting in the attic.