There was once a factory that specialised in armour. They made leather jerkins, full plate suits, greaves, helmets, anything that would stop an arrow or a sword.
One day, an order arrived from a foreign kingdom. It was a big contract, to outfit an entire army with chain-mail leggings. The factory owner was delighted, and immediately took the design specifications down to the factory floor to begin production.
Several days later, a second message arrived. Due to various circumstances, the design of the leggings had changed. The new standardised national military uniform required that the hems be lowered by several centimetres.
The factory owner grumbled about the loss of time and money involved in changing the design, but there was nothing he could do. He took the new plans down to the foreman.
Several days later, another new design arrived. The nation's uniform requirements had changed again, and the hems must be raised, even higher than the original design.