​​While making screwdriver handles during his engineering apprenticeship, he made a mistake when doing the slots around the handle circumference. He stopped and turned the rotation while the cutter was still running, forming a path on the outside of the core.

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Years later having a small CNC machine, he designed a maze that would fit around the surface of a bar.  Instead of a ball bearing, he made a pin that was in a sleeve that had to be guided around the maze.

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The requirements were:
 

1. Small enough to fit into the hand

2. Require dexterity to guide the pin

3. Have traps like the wooden puzzle above that return you to the beginning

4. Had minimum parts that were easily assembled and put the puzzle to the start

5. Was progressive and had great feedback
    

It was while thinking about the assembly, that Chris came up with the idea to have a spring behind the pin pushing it into the maze floor.  Then have a deeper channel with a ramp that stops the pin returning.  Having a deeper channel in the beginning, would allow the maze to reset quickly to the start position.

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It was soon discovered having more of these deeper channels near the maze formed the same type of trap in the wooden puzzle sending you back to the beginning.  Finally, having the maze only on one side of the centre line, concealed the maze in the sleeve while solving, making it much more challenging.