Ratchet wrench

One gear, one rocking pawl, one lever. The lever decides which end of the pawl touches the gear. That end jams one way and clicks the other.

• The pawl is a strut. Push a tooth toward its pivot and it jams solid.
• Pull the tooth the other way and it shoves the pawl aside. The plunger spring snaps it back: click.
• The lever only moves the spring plunger. The plunger tips the pawl onto its other end.
• 48 teeth: the handle catches within 7.5°, so it works in tight spots.