I can't give you the correct answer but I found a example of a skilled craft battery exam. So just go to this web address the click on requirements, then close to the bottom of the 1st paragraph click on ( see example ) .
http://www.unionpacific.jobs/careers/explore/trade/elec/ap_diesel_elect.shtml
If you're skilled in you respective field then its common knowledge
American federation of labor limited its membership to skilled craft union.
Artisans: skilled craft workers
It is a skilled job. It takes years of practice to perfect the craft.
A person who is skilled in a particular craft.
artisan
artisan.
Industrial union
by beating others and being skilled
An assistant who is assigned to learn the trade of a skilled craft worker is known as an apprentice. Apprenticeships are a valuable way for individuals to gain hands-on experience and develop their skills under the guidance of a seasoned professional in a particular trade or craft.
Artisans
Craftsman.