Depends on where you live my friend. Here in MI, we need 2 years under a licensed mechanical contractor before we can go and take our mechanical exam. Your employer here has to sign documents stating that you have worked this long and are proficient enough to take certain categories/or all in the testing....such as limited and unlimited service, gas piping etc.
“Now the freaks are on television, the freaks are in the movies. And it’s no longer the sideshow, it’s the whole show. The colorful circus and the clowns and the elephants, for all intents and purposes, are gone, and we’re dealing only with the freaks.” - Jonathan Winters