The drive cam also has a notch for different reasons.You then reverse the direction of your rotation to disengage with that wheel and turn the next to its correct position. When you dial the first number, the first wheel is rotated to a position with its notch directly below the fence. You can see why there is one wheel for each combination number.The lever moves, and the door mechanism is unlocked. When each wheel is rotated so the notch is at the top, the fence falls into those notches. Each wheel has a notch (also called a gate) at one point along its circumference.
Understand how wheel notches come into play.
