Compass Call
Over the years variations of this have been and are still used.
It was used by the RAF for Boy Entrant and Apprentice trainees in the aircraft trades.
I was pleasantly surprised that when my son was training at Witwatersrand Technicon for his National Certificate in Jewellery Manufacture and Design, they used a very similar, albeit much smaller, exercise.
The common thread is that you are never have the 2 pieces in your hand until you try to fit them together.