You might think, well, they'll just turn together and that's a completely useless device, but he made this very critical discovery, that the gear with the pin turns on a slightly different axis than the gear with the slot.
Moglo bi se pomisliti da će se samo okretati zajedno i da je uređaj potpuno beskoristan, ali otkrio je nešto presudno, zupčanik s klinom okreće se na malo drugačijoj osi od zupčanika s utorom.