OTJ training. And a natural knack for taking things apart. Hey, if it's already broke now...
I took apart an heirloom mantle clock when I was about 10 or so - had it all apart on the living room floor b/c it didn't "gong".
Dad came home from work and just said I'd better be able to put it back together. I did, and it "gonged".
Been fixing things ever since.
@FireMonkey
It is a wonderful skill to have.
As a kid hubby took out the motor of the family lawnmower and built a go cart. I’m not sure that went over well.