Edited sentence: Finally, he was able to use interchangeability of parts which was essential.For one, it used domestic natural resources, Ford also produced cars for middle class Americans.He didn't have any specialized training in engineering, he just had basic knowledge of reading, writing and basic math.It was very basic, but becasue there was no customization, it made it cheaper to produce, making it available to more people.Like earlier state, the use of the assembly line was essential and reduced the time to put a car together from 12 hours to 1 1/2 hours.The production methods developed by Ford came from basic schooling that was available to all children.There are five main reasons why the Ford's automobile was so important to the U.This made it so that if something on the car broke or stopped working, it could easily be replaced without the need for a fitter.Unlike Europe, where cars were highly specific for each consumer, Ford produced one car at first and it only came in black