Craft unions, like in construction, are more like guilds than the industrial unions. You must qualify in one way or another to be a union member before you can

Craft unions, like in construction, are more like guilds than the industrial unions. You must qualify in one way or another to be a union member before you can get hired by a union company. But in an industrial union, as an example get hired by an automaker with a UAW contract (and not in a so called right to work state), you are a UAW member.