How It Works (The Dialing Process)

Let's imagine a common three-number combination lock (e.g., 25-50-75):

1. Scrambling and Picking Up All Wheels:

   • You start by turning the dial several full rotations in one direction (e.g., clockwise). This ensures that any previous alignment is completely scrambled.
   • As the dial turns, the spindle rotates the drive cam. The drive pin on the drive cam will eventually engage the drive pin (or "fly") of the first wheel in the stack.
   • This action continues down the line: the first wheel's drive pin picks up the second wheel, the second picks up the third, and so on. After a few full rotations, all the wheels will be "picked up" and rotating together with the dial.

2. Setting the First Number (e.g., 25):

   • You continue turning the dial in the initial direction (e.g., clockwise) until your first combination number (25) aligns with the indicator mark.
   • When you stop on this number, the gate on the outermost wheel (the one furthest from the dial, and thus the first one picked up) is precisely positioned. The clever part is that the drive pins are designed so that when you reverse direction, this wheel remains in place.

3. Setting the Second Number (e.g., 50):

   • Now, you turn the dial in the opposite direction (e.g., counter-clockwise). As you pass your first number (25) at least once, the drive pin on the drive cam will engage the next wheel in the sequence.
   • You continue turning until your second combination number (50) aligns with the indicator mark. This aligns the gate on the second wheel, while leaving the first wheel's gate in its set position.

4. Setting the Third Number (e.g., 75):

   • You again reverse direction (e.g., clockwise). As you turn, the drive pin will engage the third wheel.
   • You continue turning until your third combination number (75) aligns with the indicator mark. This aligns the gate on the third wheel.

5. Unlocking:

   • Once all the numbers are entered correctly, and you stop on the final number in the designated direction, the notches (gates) on all the wheels will be perfectly aligned in a straight line.
   • This alignment creates a clear gap or "channel" directly underneath the fence.
   • The fence, often under its own weight or spring tension, drops into this aligned channel.
   • When the fence drops, it disengages from the locking bolt or hasp, allowing you to move the bolt (e.g., by turning a handle or pulling the hasp) and open the lock.

Relocking

To relock the mechanism, you simply turn the dial a few full rotations in any direction. This action causes the drive pins to re-engage all the flies on the wheels, deliberately scrambling their alignment and lifting the fence out of the gates, thereby securing the lock once more. This ensures that the combination must be re-entered to open it again.