This Mariano story from Michael Young is a little “inside baseball” & hilarious
Here’s my Mo story... We’d have the guy in the on deck circle use the metal donut. If Jorge set up inside he’d knock the donut off hard, hitter would hear it, and know it was cutter inside...ya, not very obvious. It worked. He’d get 3 outs on 12 pitches instead of 9. Congrats Mo!