Possible Clues:

• Move by degrees in one direction only
• Chatter (anag.)
• Mechanical device that could make one chatter
• Couple of scoundrels, second of which knocking out a tool
• Increase incrementally, with "up"
• Device stopping backward motion
• Gradually increase, with 'up'
• Mechanical device used by fantasy author, not the first or the last
• Rodent caught by the unusual mechanical device
• Mechanism in a unidirectional wrench