Many, MANY years ago, I was learning Model 28 Teletype repair on the job. The guy that was teaching me was good and I was picking it up pretty well. I took a page printer apart for quarterly maintenance and laid all the parts and subassemblies out on the bench like an exploded diagram.
"Good job," Larry sez and handed me some quarters. "Here, go get us a soda and you can put it back together after we take a break."
I ran up to the soda machine and when I came back Larry was standing there with a s**t-eating grin on his face, shaking a burn bag full of teletype parts.
Took me 4 or 5 watches to put that thing back together, but I did it and it worked perfectly. I learned more about teletypes in that 4-5 days then I did the whole 4 or 5 weeks preceding. I bet I could still do it and I haven't touched a TTY in 40 years.